Poke-what???

So what's the deal with these Pokemon cards. Bryson is obsessed. He eats, walks, and dreams Pokemon. Seriously, he does nothing else unless I take the cards away from him, and then he pouts his way through his homework and chores (and if you know Bryson, you know that when I say pout, I mean that he pouts with his entire body). He tried explaining them to me and told me what all the numbers mean, but I am totally lost. If anyone out there knows the story with these crazy cards, HELP!