Magic is what sets folks in the wizarding world apart from their Muggle neighbors. Magic is the heart and soul of the wizarding culture in the same way that science and technology are the heart and soul of Muggle culture. Where a Muggle would pound a stake into the ground using a sledge hammer (a simple machine), a wizard would use a wand. Both the Muggle and the wizard view their choice of tool as completely and utterly logical and ordinary, although each would find the other's tools fascinating and even mysterious.
The basic concepts of magic are fairly simple -- even a two-year-old wizard can do some form of magic -- but the inherent power and potential for misuse are great indeed. It is for this reason that promising young witches and wizards are sent off to Hogwarts and other schools of magic to refine their craft and learn the art and responsibility of their power. At Hogwarts, students learn a variety of magical specialties as well as general theory and the history of magic in their world.
"I don't believe in witchcraft, though I've lost count of the
number of times I've been told I'm a practicing witch. Ninety - let's say
ninety five percent at least, of the magic in the books in entirely invented
by me. And I've used things from folklore and I've used bits of what people
used to believe worked magically just to add a certain flavor, but I've
always twisted them to suit my own ends. I mean, I've taken liberties with
folklore to suit my plot."
Rowling spent the first five years of creating the Harry Potter books working on "the rules" for her fictional universe. She doesn't spell out these rules in the books, but she drops plenty of hints. In order for the ordinary "Muggle" reader to better understand the way things work in the world she created, the Lexicon presents a series of essays detailing these rules, as far as we can discern them. None of these essays was written by Rowling herself, but each is based on careful analysis and interpretation of events in the stories.
Wand, Word, and Will: How Magic Works
The Complete Guide to Magic provides a complete guide to all the magical spells, devices, potions, and terms (as well as links to the Lexicon's individual encyclopedias and directories for specific areas of interest).
History of Magic