Actions turns your iPad into a remote control for your Mac. No, it’s not a VNC app which lets you project your desktop onto your tablet’s screen. Nor is it a media remote (although it can be). Instead, Actions lets you assign, uh, actions to easy-to-tap tiles on the iPad’s screen, and these actions are then performed on the Mac (or PC).
The short version: Actions lets you trigger Mac keyboard shortcuts from your iPad.