Print Screen on Mac?

Hi,
I've looked at my MacBook keyboard, and I cannot find the button to do a print screen? If you don't know what I am talking about, I mean the thing on windows where you can press a button or two and it turns your screen-shot into a .jpg, or something along those lines. How do you do this on Mac - or can you? Thanksssss.

apple shift 3 = capture entire screen
apple shift 4 = capture part of screen
apple shift 4 then space = capture selected window