The Flyblack function means that the chronograph hand can be reset to zero and immediately started again by pressing once the pusher. That’s why there are two hands for the chronograph.
Chronograph watches can measure and display elapsed time. Usually three subcounters on the dial display the elapsed seconds, minutes and hours.
Watches featuring a « big date » display an oversized window and have two independent date discs.
The date is a small window on the dial which indicates the day of the month (between 1 and 31).
Watches featuring a small seconds have a smaller subcounter, usually located at 6h, which indicates seconds.
The power reserve indicator tells you the time the watch will continue to function. It can either be seen on hand winding or automatic watches.