Whilst anyone can practice magic, witches (normally, exceptions do exist) have greater knowledge and power over harnessing mystical forces. Witches have existed for many centuries, and are found in many races' lore.
Witches commonly form covens, but this is not a necessity. They are also often social, and meet with other witches.
Although witches aren't inherently evil, most nonetheless often turn evil (or at least have moments of disregard) as their power can corrupt them, or they make deals with demons for more in exchange for their souls. Dean compares it to crack, stating that once they get it, "it's surprising what they will do."
They are split into three types, depending on how they gain there powers:
The Borrowers
The term "Borrower" is commonly used to define any person who has obtained their power through demonic forces. These witches are known to have summoned demons and made deals with them in exchange for power. While it common for these witches to have exchanged their souls in trade for power, it has been implied that not all Borrowers sell their souls, but rather promise something else of value to the demon. According to the witch Rowena, these witches are very common and make up for more than half of the witchcraft community.
The term "Natural" is commonly used to define any person who has obtained their power from biological development. Not much is known about these witches apart from the fact that they are known to have been born with a natural affinity to the supernatural powers of the universe. According to the witch Rowena, these witches are very rare and make up for less than half of the witchcraft community.
The term "Student" is commonly used to define any person who has obtained their power through practice and training from other witches. According to the witch Rowena, these witches are less common than Borrowers, but more common than Naturals.
There are significant differences in power between witches, with some being powerful enough to stun even low-level Leviathans, while others can hardly even defend themselves against human attackers. As such, not all witches have the same abilities. Below is a list of powers demonstrated by different witches over the course of the show.
Spell Casting - The act of changing and/or controlling events through the use of charms, hexes, rituals, etc. Powerful witches like Don Stark can easily cripple a Leviathan, however he states he can't kill them. Witches commonly require rituals and objects to direct the spells, such a Hex bags, or enchanted objects like Tarot cards or coins.
Hexing - A common use of magic; this causes the person at whom the spell is aimed to die by manipulating the environment around them.
Telekinesis - The act of controlling and manipulating the movements of objects and people by mere mental influence.
Electrokinesis - Some witches may be able to generate electricity through a spell, though it is not proven. File:Bolt.png
Spencer casting a bolt of magic against James.
Biokinesis - Some witches can use magic to manipulate the human body.
Tracking - Some witches can use magic to track down others.
Summoning - Some witches have used spells to summon demons.
Reality Warping - Some are able to alter reality through magic, but this is usually only to a very small degree.
Longevity - Some witches have been shown to live much longer than typical humans. Some are even potentially immortal, but they can still die as easily as normal humans, provided the attack can get through any invulnerability spells.
Astral projection - One witch was able to project both his own awareness as well as those of Sam and Dean out of their bodies. Another was able to use a spell to spy on her son.
Memory Manipulation - One witch was able to transfer memories into the mind of another witch. He was also able to bring forth memories of Hell and Lucifer's cage in Dean and Sam respectively.
Granting Invulnerability - One witch was able to charm himself so that he survived being hit by a car without a scratch, and also implied that being hit by bullets would only tickle him.
Teleportation - One witch showed the power to teleport over short distances.
Super strength - One witch was strong enough to lift a full-grown familiar into the air and slam him down with ease. Another was strong enough to rip victims to shreds with his bare hands.
Potion Brewing - The act of brewing and concocting paranormal elixirs that contain supernatural properties.
Tools
Grimoires - Certain witches use books and tomes that provide instruction on incantations, spells and sigils.
Book of Shadows - A magical book documented with ancient magical knowledge, rituals, and spells. This was carried by Astaroth in recruiting new witches.
Candles - Materials used to amplify a witch's spells.
Hex Bags - Materials used to curse, kill, enchant or protect another person.
Herbs and Roots - Materials used as ingredients for brewing magical potions.
Weaknesses
Iron - It appears that some of, if not all, of a witch's powers can be blocked with iron, as James couldn't astral project until his iron chains were removed. Likewise, he most likely couldn't use magic to escape, as he asked Dean and Sam to remove the iron chains(though it should be noted that astral projecting transforms one into a living ghost, and ghosts cannot cross iron).
Magic - While most witches have been known to cast protection spells upon themselves, some witches are still susceptible to magical influences.
Witch Killing Spell - A spell that Bobby Singer taught Sam and Dean Winchester; once prepared, it kills any witch it hits, and makes it impossible for them to use magic to protect themselves. It has a very small area of effect, as it killed one witch but left another who was standing only a few feet away unharmed.
Mortality - Based off the fact that witches are still human, they share many of the same weaknesses as non-supernatural beings (e.g. age, decapitation, disease, heart-failure, suffocation, etc.). However, it is known that especially powerful witches can overcome these weaknesses.
Trivia
Dean and Sam Winchester have the poorest record against witches. Thus far, only three witches have been defeated by the Winchester brothers specifically. More often than not, witches are killed by other creatures such as demons or other monsters.
While some witches are known to have familiars, the majority of witches do not.
