Photo or video? or both?
Make sure you have a solid understanding of:
^Those are the absolute core essentials
As far as 'What camera should i buy?'
What are you using it for? Chances are, youre gonna buy a T2i, which is an excellent place to start. But if you dont do your homework first, it'll just be an expensive paper weight.
Here's some of the stuff you can read about, and also learn with practice:
PLEASE DONT BUY THE KIT LENS
Read forums on here and other photog/video sites, find the lens thats best for you.
Great lens to start with is the Tamron 17-50 2.8
Depth of Field
how aperture affects it)
i know im missing a shitload of info, but at least you got something to start with