Witchcraft is, exactly as the word implies, a craft, something which must be learned and practiced in order to achieve mastery. It's no different than quilting, sewing or woodworking in that manner. In order to BE a quilter, one must learn to quilt, and perfect their craft through practice. One can not simply read a few books on the subject and decide one is a quilter without ever lifting a piece of material. Witchcraft is similar, Religion, on the other hand, is not. If one reads a few books on a religion and decides that this is what they believe, they can in fact take the title which this religions followers don. For example, if one reads the Bible and says "This speaks to me, I believe in Jesus, I believe in YHWH, and I feel this is my path" they can then call themselves Christian -- it should however be pointed out that there is a difference between an Active member of a faith and a Passive member, but that's a different post. Religion is about belief more than it is practice. And while there are those who will argue this point, the fact is there are hundreds of thousands of Christians out there who truly believe, who have a very sincere faith, but who lack the practice - NO ONE would deny however that they are Christians by definition. Because that's what Religion is - belief. If you believe in what a religion teaches, you are - in one way or another - a member of that religion. Witchcraft, however, doesn't work that way. You can read 1000 books on Witchcraft, but if you never practice, you still aren't a Witch. It's not something you just believe, it's something you do!
Additionally, Witchcraft is NOT limited to any one religion. Witches - although they don't always take that title - exist in EVERY religion on Earth. Shaman, Medicine Man/Woman, Curandero, and numerous other titles and terms have been used as an alternative to the word for those who practice Witchcraft. Depending on the culture, these titles may mean different things, and at times or places (such as in the US) they can denote different types of practice, specific influences or abilities.
So what IS Witchcraft and how do you know if you're practicing it? Well, that is a more complicated question. Witchcraft is an "umbrella term" which encompasses a great many magickal arts. These "arts" are often termed by Occultists as "Low Magick" as opposed to "High" or "Ritual Magick." However, in today's Pagan religions, there has come to be a blend of both these "High" and "Low" forms which has resulted in an even broader meaning.
Generally, "High," "Ceremonial" or "Ritual" magick is generally defined as a magick in which the practitioner uses specific rituals and invocations to call upon the spirit world in an attempt to gain knowledge, power or control spirits or other entities. Those who solely practice this form of magick are often termed "sorcerers" rather than Witches. Of these, the most famous by far is, of course, Aleister Crowley. When we look back through history, it is THIS form of magick which was most revered and feared in most cultures, with famous (and often imfamous) names such as Merlin,Simon Magus, Abramelin the Mage, and Eliphas Lévi still being linked with both wondrous and sometimes frightening workings. When I was first studying the Occult as a teenager, I happened across one story which nearly frightened me out of practice altogether. It was a story of a Mage who's "houseboy" had been killed when attempting to summon a demon without his masters presence. Now, whether or not this story was true, I do not know. I have never again found it, nor have I found another copy of the text I was reading (that's a long story in itself). BUT, it does speak towards the type of magick which "High" Magick sometimes includes. That said, High Magick is in NO WAY Evil! Although, like all magick it can be used for nefarious means, it is the practitioner who dictates the use and outcome.
High Magick HAS greatly influenced modern Witchcraft though. Wicca and numerous other Pagan faiths encourage their practitioners, even those practicing solitarily, to preform or partake in some form of Ritual Magick in order to honor their Gods/Goddesses, specific Sabbat or moon phase or even as a way of preforming every day magick. However, it is important to note that for the most part, the Rituals preformed by the average Witch are NOT the same as those practiced by High Magicians of the past. They are usually NOT attempting to raise or control beings, obtain great power or alter the state of the world in any major way as High Magicians of the past (and present) are known for. There ARE, however, a great few modern Witches who are ALSO High Magicians - but this is an exceedingly small percentage.
So, now we know what "High" or "Ritual" Magick is, but what is "Low" Magick? What is "Witchcraft" if it's not technically "High" Magick? Well, "Low" Magick is not considered "Low" because it's any less powerful. Nor is it in any way inferior to "High" magick. It is, however, the type of magick which has come to us through the every day practice of every day people. It requires no specific tools, no magic circle (although due to influences talked about above, many today use one) and no specific words. Instead, "Low" magick is the type of magick which just about anyone can do at any time. This is the type of magic used by Medicine Women, Shamans, Cunning Folk and every day housewives for centuries.
Low magick, witchcraft, is generally defined as "The Use of Energy to Create Change." This can be done in at least 1000 different ways. Some of these ways could be as simple as focusing energy into solving an issue (which really isn't as simple as it sounds) or using the power of herbs to heal a wound. Some of these ways could be as complicated as using one's Astral Body to travel into the Otherworld and seek answers from a long lost relative... It's fair to say that just as High Magick takes years of education, training and practice to "master," Low Magick or Witchcraft does as well. The one major difference is however, that even a first time Witch can successfully carry out her magick, depending on what she is attempting to do, while the attempting High Magick without training can be dangerous.
Some forms of Witchcraft may seem less "Magick" and more "Mundane." And in fact many of these have taken hold in what seems to be mundane parts of our society today. Herbalism, Crystal Healing and numerous forms of Energy Work are now available through "Healthcare" establishments and are sometimes even covered by health insurance. And while you won't hear most of these practitioners use the title "Witch" when describing themselves, they are using (and usually knowledgeable about) the same principals that a practiced witch would when relying on these forms of magick. The DIFFERENCE between your average Crystal Healer or Herbalist and a Witch is the use and focus of energy. An Herbalist will prescribe herbs based on the needs of the patient and the medicinal properties of the plant. A Witch will do the same, however, the witch takes things a step further by not simply relying on the plant's healing properties and infusing the remedy with energy focused on healing the patients ailments or creating good health.
Other forms of Witchcraft are clearly not mundane and are often portrayed by Hollywood as supernatural. I think the most commonly shown forms include Poppet (doll), Candle, Knot magick. These forms are however, neither "supernatural" nor less magickal than others. Like the use of herbs or stones, these forms of witchcraft require the witch to focus energy onto an issue in an effort to create some kind of change -- The only real difference is HOW she chooses to go about this.
Additional forms of Witchcraft do not generally fall under the category of "Magick" but are none the less, witchcraft. These include forms of divination, spirit/fae communication, astral work, dream-scaping and other forms of spirit, astral, and etheric working... Again, these practices come to us from a number of sources, but most come from the practices of "witches" of the Old Religions/Cultures. Some of these were reserved purely for the most adept Shamans, others were common practices among the "laymen" of PreChristian (usually Native American or European) Cultures.
While ALL of these practices may, or may not, be included within various religious teachings, they are generally reserved for only the highest religious authorities or taught in addition to religious theology, ethics and/or practices. Even those faiths which are occasionally (and mistakenly) termed "Witchcraft Religions" do not require practitioners to practice or master ANY of these forms of Witchcraft. Many of these religious groups DO, however, expect practitioners to either personally preform or participate in some forms of Ritual or Ceremonial Magick -- usually surrounding "Holy-Day" or other celebrations. Wicca, for example, expects coven members, as well as solitary practitioners, to participate in Sabbat Rituals which often invoke and honor specific deities or spirits. Wiccan Full Moon Esbat rituals often include what is called "Drawing Down the Moon" where a practitioner will draw into herself the essence and energy of the Moon Goddess/God. While these are NOT Ritual or High magick in the "classic" sense, they are - as discussed above - the result of High Magick's influences on new modern magickal traditions & religions.
I WILL say that most of the followers of these "Witchcraft Religions" do actively and intentionally practice Witchcraft in one way or another. But there are those who don't, for one reason or another.
Religion, as I have discussed in he past, is defined as:
"a set of beliefs concerning the cause, nature and purpose of the universe, especially when considered as the creation of a superhuman agency or agencies, usually involving devotional and ritual observances, and often containing a moral code governing the conduct of human affairs." (definition provided by Dictionary.com)In short, religion is belief! Whatever your beliefs about the cause, nature and purpose of the universe, and especially if those beliefs include spirit beings or god(s) and include a moral code of some kind, THAT is your Religion -- even if you are the ONLY one who believes it. Organised Religion is simply a form of religion which is created, dictated and taught to a group of individuals who mean to adopt it's ideals, and teachings as their own. So, if you believe, you belong. Although some will argue if you don't practice what you preach you're not a "REAL" member of your religion, and that's somewhat debatable, especially with so many variations of most Organised Religions out there. But, in general, if you believe what Christianity teaches, you're Christian. If you believe what Islam teaches, your Muslim. If you believe in what Wicca teaches, your Wiccan.
Witchcraft, on the other hand, doesn't work this way. All of those types of Witchcraft I talked about above, require a good deal more than simple belief. It is important here to point out that if you don't believe, witchcraft won't work for you, but that simply believing it will is not enough to make it work if you don't have the skills to back up that belief.
So simple answer: NO Witchcraft is NOT a Religion. There are those religions which encourage Witchcraft, and there are those which discourage it. However, you can be a member of ANY Religion and practice Witchcraft (although you may choose not to call it that if you belong to a faith which discourages or bans it.)
**Please note that while I use the terms "she" or "her" here when speaking about Witches, this is simply out of ease. No disrespect is meant to my brother witches.