Unfortunately it's a bit of all of them. There are multiple ways to take screenshots on a mac depending on what you're after: Cmd-Shift-3: takes a full screen

Unfortunately it's a bit of all of them. There are multiple ways to take screenshots on a mac depending on what you're after: Cmd-Shift-3: takes a full screen shot. Cmd-Shift-4: gives you a crosshair to select a portion of the screen. Cmd-Shift-4 + Space: gives you the crosshair, and pressing space allows you to select individual windows to screenshot. All of the commands above will save the resulting screen shot to the desktop. If you add Alt to any of the commands, it instead saves the shot to the clipboard. (So the OSX equivalent to the "Print Screen" button in Windows is Cmd-Alt-Shift-3)