Okay, I'll try and explain them as best I can, but I'm not great at explaining...
EVs: Each Pokémon, when defeated, gives specific EVs (Diglett gives 1 speed, Abra gives 1 Special attack). For each 4 EVs you get in a stat, you'll have 1 more point than normal by Level 100. You can have at most 510 EVs, and 255 in one given stat.
Here's an example:
Level 100 Alakazam w/ Neutral nature (& max IVs, which I'll explain soon!)
0 Sp Atk EVs: 306
252 Sp Atk EVs: 369
Why 252, you might ask. Well, 255 isn't divisible by 4, so the extra 3 are wasted if I made it 255, so a general rule is to put no more than 252 in a stat!
IVs: When a Pokémon is caught/hatched, it will have a hidden number in each stat, from 0-31. This is added to there stat by level 100. Going back to our Sp. Atk Alakazam, he would have:
369 Sp. Atk with max IVs
But only 338 with no IVs.
Basically, between IVs and EVs, you can add 94 to two stats, and 31 to the other 4!!!