adb the Android Debug Bridge establishes the connection to the device as via USB. It is used for development purposes and to control and manipulate files on the device via PC. It usually has to confirm on the devices screen that adb is permitted to be used.

Under Gentoo Linux it can be installed using emerge android-tools

It brings the following applications :

adb requires to be connected with the android device typically via USB.

See https://wiki.lineageos.org/adb_fastboot_guide.html and https://wiki.archlinux.org/index.php/Android_Debug_Bridge

lsusb shows the devices lsusb -s 2:5 just the device on bus2 device 5 that has previously been identified as the phone lsusb -s 2:5 -v gives then the verbose info where idVendor and idProduct can be spotted:

If done, as regular used do adb devices where the phone should be listed.

adb shell gives a Linux shell on the PC

adb shell ls -la /sdcard/DCIM/Camera lists photos