Android debug bridge (adb) is a versatile tool lets you manage the state of an emulator instance or android-powered device. it is a client-server program that includes three components:
a client, which runs on your development machine. you can invoke a client from a shell by issuing an adb command. other android tools such as the adt plugin and ddms also create adb clients.
a server, which runs as a background process on your development machine. the server manages communication between the client and the adb daemon running on an emulator or device.
a daemon, which runs as a background process on each emulator or device instance.