This is another something I wrote up in response to someone asking about Paganism. It is by no means a complete intro, but I figure if anyone ever asks “What is Paganism” this is a very simple answer, especially the first paragraph.
Do you know the stories of the Greek, Roman, Norse, Celtic, and other Gods and Goddesses? Paganism is the revival and practices of those deities, just as the Jews, Christians, and Muslims practice their believe in their God. Another key thing is that Pagans believe in Magic, that is real, and that it can be used. However, not all Pagans practice magic, the level of Magical learning and use is generally up to the person. Most, however, do seek at minimum a passing knowledge, and many of those seek deeper practice.
There aren’t really anything in the way of churches. Pagans have Temples, though there are very few of those to date. One I know if the planned Asatru (Norse Pantheon) temple in Iceland. There are however lesser holy places such as groves and areas like that where some groups do gather. Most Pagans, however, tend to be solitary or form small groups at this point in time.
There are two main paths in Paganism: the Soft Polytheists who believe that all gods are aspects (or faces) of a singular Male God, and all the goddesses are aspects of a singular Female Goddess. The other group is the Hard Polytheists, who believe that all the Gods, Goddesses, and other spiritual beings, are their own Individual Beings.
Inside the umbrella of that, however, are many different variations. For every pantheon out there, there are those who can run the line from “I’ll Take Everything” (meaning that any practice that catches their eye or feels right gets folded into their practice) to the “Documentation Only” (meaning that they take only that which was historical to their pantheon/culture and nothing else. The people are also known as Re-constructionists, Recons, or Heathens, and their main branches are Norse, Germanic, Celtic, Roman, Greek, and Khemetic/Egyptian).
If you’re interested in getting into Paganism, the best place is to start with books and some websites.
There’s a ton of Wicca 101 Books out there. A fairly good book if you’re interested in the Norse is Essential Asatru by Diana L Paxson. A really good website is Walking The Hedge by Juniper and it part of a larger site with forums and other resources that will help in discovering more about general Paganism. From there you can always follow links and such into the wider pagan web. Read blogs, be respectful, and browse your local bookstore (you might not be able to find much in a physical bookstore these days, unless you have an “occult” shop that sells them). You can always specialize later into Wicca, Asatru, or the other many branches of Paganism.