Will PS2 games play in a PS3?

So I've read that PS2 games WILL play in a PS3.. I'm a horseback rider & I want some horse games and rodeo games but they are all PS2... I would like to have a final answer if the PS2 games actually will work in my PS3.. I know that you can buy something that will allow you to use PS2 games in the PS3 but what is it.. Thanks soo much!