Keep reading! All will be revealed! That's the fun in reading!
I just started reading Harry Potter, and I'm a little confused. How exactly is Harry a half blood? Weren't both of his parents wizards? And what exactly is the difference between a half blood and a mudblood?
You've just started reading the best series of all time!!! The answer to your question makes perfect sense if you continue reading. Don't spoil it for yourself!