Yes. I mean I know what a Pokemon is, but I don't know what the gameplay is like.
Oh, okay. For a moment there I was extremely concerned.
Gameplay is basically this: You get a starting pokemon, and use it to fight other, wild pokemon that you encounter by walking around in circles in tall grass and caves and shit. When you get those wild pokemon down to low health you can capture them using a pokeball and then use them as you please. Pokemon level up as they fight, gain new abilities, and evolve into more awesome versions of themselves.
There's some strategy involved - different pokemon have different elements (fire, water, etc) that are SUPER EFFECTIVE or not very effective against certain other elements, and there are various status buff/debuff abilities as well.
Edit: see Celes' highly informative educational video.