adb stands for android debug bridge which is used by most of the developers for finding bugs in their Android devices by connecting their device via USB to their system. this make sure that you have turned on the USB debugging mode on your Android device.
to use adb you'll also be going to need SDK which stands for Software development kit and your device drivers. so if you want to root your device you can use these techniques.
the whole adb process goes by command line. don't worry if are not aware of the commands, some websites provide line by line instruction on how to use adb, you just need to copy paste those commands in order to make them work.