riding disciplines?

[Cynnycal]

i want to learn what the different types of riding and competition there are. i mean, i know there's dressage, hunter/jumper, eventing, reining, etc. but i don't know what they entail.
right now i am just learning basics, english pleasure i suppose you'd call it.
does anyone know of any sites, articles, etc. that explain basics of various different equine sports?