Grab is an OS X system utility that allows you to take screenshot of the desktop. The app is located under /Applications/Utilities/ folder. To start a timed screenshot, select from Grab app menu Capture > Timed Screen or hit Command-Shift-Z.
From the popup window, click on “Start Timer” button to start the 10 seconds count down timer. Stage your desktop before Grab snaps the entire screen. Grab will not be visible in the final captured screenshot.