The recovery menu is a special menu for forcing upgrades (MCU or android system) when the unit is not working properly (like stuck on logo).
It is part of the recovery partition. Recovery mode has capability to access some core functioning in the device, such as Resetting the unit, Data Cleaning, Installing updates, Backup or restore your data, etc.
This menu can be accessed by using a clip or a needle to press the physical reset button (pin hole).
Android 10 and above:
Press the reset menu and the unit will be shut off....hold pressing it for about 15-20seconds until you see the booting logo...after that the recovery will appear.
Video:
For android 9 and below:
Press reset button and you will see the unit switch off...hold it pressed until you see the unit button lights blinking....release the reset button and press it again for about 5 seconds and release again. The booting logo will appear and then the recovery menu.
Video: