How to use Nikon D5000 self-timer delay?

There is a FN on the fuselage, which can be set to press the shutter for 2 seconds, 5 seconds, 10 seconds, 20 seconds, and then release the shutter. Mainly used for self-portraits, or to reduce low-speed jitter.

In the case of time-lapse photography, one photo is taken every x times, usually in a fixed position or a regular moving position, and then y photos are taken and then played in turn to form a video. Suitable for shooting clouds, flowers, boats, etc.