What Does The Adb Command Do Within An Android Device's Shell?

I was connected to my Android device's shell (by doing adb shell in my computer's shell) and without realizing, I typed adb devices. Instead of giving me a command not found error

Solution 1:

Some phones do include the adb binary. Some for a specific purpose, others just because the manufacturer was too lazy to edit the default makefile.

Also adb devices listing an offline instance of an "emulator" does not mean that there's an emulator running on the device, just that there is an open tcp port in the range that adb scans when looking for emulator instances. Just ignore it.

Solution 2:

Don't worry about emulator.Emulator creates a virtual android device. By using this facility a programmer can test his code on computer without connecting any device. You can read about emulator from https://developer.android.com/training/basics/firstapp/running-app.html#Emulator.