Chronographs are watches that have additional timing functions. A standard chronograph usually has a sweep second hand that can be started, stopped, and returned to zero by successive pressure on the crown. These are handy for timing events. Other chronos have independent hands (usually in subdials) to measure seconds, minutes, hours and even tenths of a second. Many chronographs have moveable bezels that allow you to calculate speed or distance. And of course, some just like the look of the extra subdials and other features that give the watch a high-tech look, even if they seldom use the extra functions.