*bounces* Thankyou! I'm glad things are making more sense now. ;>_> The HP world is fairly simple:

Magical people living in secret from normal society.
Evil magical overlord trying to establish himself as being in change and want to kill everyone who isn't a 'pureblood' (wizards and witches can be from magical lineage, but they can also just pop up randomly from two non-magical humans. The 'purebloods' don't want the 'muggleborns' muddying up the bloodlines - this concept can be compared to Nazi ideals)
Evil overlord kills Harry Potter's parents when he's only one, intending to kill Harry, too. Unfortunately, because Harry's parents sacrificed their own lives for him, he was protected by an ancient spell which means that Voldemort can't kill him.
Voldemort sortof-dies when his magic rebounds as he tries to kill Harry.
Harry is sent to live with his muggle relatives who abuse him because they are afraid of magic. (they don't tell him he's magic, either).
Harry eventually goes off to Hogwarts, a boarding school for magical children. There he makes various friends (and enemies, namely, Draco Malfoy) and thwarts Voldemort's plans to bring himself back to power several times.
When Harry is 14 Voldemort uses Harry's blood in a spell to return him to his body. (he uses Harry's blood to devoid the magic that protected Harry.)

But I daresay you already had figured out most of that. I guess what trips you up are the finer details and you'll have to read the books for those. *pokes tongue at you*