found such jumpers on the motherboard, and it became interesting. what it is? what are their names? What are they for? Where exactly to insert them? why not on all motherboards are located?

Answer 1, Authority 100%

In the image:

Left – Clear RTC, Resets CMOS settings (BIOS).

Right – Switches the system unit to + 5VSB mode (Standby) in which the power on the 5V bus is supplied even when the computer is turned off (for Wake-On-Mouse / Keyboard / LAN functions)

In the documentation for a specific motherboard, the functionality of each position for the jumper will be painted.

Answer 2, Authority 50%

These are jumpers (literal translation of the word Jumper, there is a hardware slang – “jumper”). Used for various settings, but the most popular jumper is now, perhaps, the CMOS reset (is required if it is not possible to enter the BIOS, for example, with an unsuccessful processor acceleration). Previously, the jumpers were more common, but now most of the settings went to the BIOS and is managed programmatically, which is incomparably more convenient.