"Here is the list of MAC Print Screen Tricks/ Shortcuts that would allow you to use Print Screen in MAC.
Overview
You just broke the highest score in your favorite game and want to keep a screenshot of it to share it with your friends. You have done it in a PC, but you using a MAC now. How do you do it?
Unlike Windows PC, MAC doesn't have a dedicated Print Screen key on its keyboard which makes it hard for new MAC users to perform screen capture. This article comprehensively details every possible free method to use the Print Screen Feature in MAC. These methods include using keyboard shortcuts and bundled Apple utilities."
Want to create a screenshot suitable for saving or printing? Then just hit a key on your keyboard. Oh yeah, you'll have to download this program first.
There are several hotkey combos to choose from (PrintScreen is the default). Once you've chosen your favorite combo, head to the Destination tab and have the screen print out instantly, copy the capture to the clipboard, save it to a specific folder, or even send it through e-mail. You can perform full screen captures, or only capture a specific window.