So the game places pokemon around you using the geopositioning on your phone. You have to turn your phone's camera on and scan for them. So as you're scanning around with your camera the game will superimpose a pokemon into the picture. I guess certain types of places have more pokemon than average, like parks, churches and other public places. So if you go to those places you'll most likely find more pokemon. I think the goal is to collect them, but first you have to find them. Like the girl that found the dead body, she went down by the river looking for water type pokemon (that only live by water, apparently) and she ended up finding a dead guy instead.