What does f2 do?

Hi this is probably a really stupid question but I accidentally pressed f2 on my keyboard and now there are the green numbers appearing on my screen. They change colors when I give input how to do make them go away? Thnx (:

To my knowledge, F2 is not a Unity hotkey, so this is probably some other application you have running in the background. Screen Capture/FRAPs?

If I press F2 when clicked on anything in the hierarchy or project manager it renames the file or object.