Self-timer

A manual self-timer, 2011.
A manual self-timer mounted on a film camera, 2011.
A self-timer drive mode button on a Canon digital camera, 2008.
Robert Faries: Shutter tripper for Camera's, US Patent 690,939, January 14, 1902.

A self-timer is a device on a camera that gives a delay between pressing the shutter release and the shutter's firing. It is most commonly used to allow the photographer to take a photo of themselves (often with a group of other people), hence the name.