Is there a print screen function on mac keyboards?

There is no print screen key for Macs, however, there are several key combinations for taking screenshots based on what you want to do with the screenshot.

I personally use Cmd+Shift+4, and select what I wish to take a picture of, or if i want to take a picture of a window, I press space. This will save the screenshot on your desktop.

However there are several more available, see related links.
On the keyboard