Decide if you want just the right time or if you want something more than the whistles and bells
See the measurement functions (with the exception of hours, minutes and seconds) are called "complications". The most well-known complication watches calendar watches, the most common of which only the date. There are also Chronographs with center second hand, which can be started, stopped and reset to zero with one or two buttons on the side of hours. Other additional functions include second time zone, alarm clock, moon phase, repeater, perpetual calendar, etc.
A chronograph is a watch that not only time, in hours, minutes and seconds, but a continuous and discontinuous intervals. Basically, it watches with stopwatch function.
Chronometer is a precision clock movement, after rigorous inspection, have an official certificate from the official list of the dates of the bureau. Is the precision instrument, which, together with the certificate.