adbd is the Android Debug Bridge demon which manages communication between a computer and an Android device (or emulator instance). This tag is appropriate for problems with getting the demons to run. Problems with using the adb client program should go under the [adb] tag.
There are two demons of this name: one runs on every Android device with developer mode enabled (and in the Android emulator), and the other runs on Linux, macOS or Windows machines being used for development, or with adb installed for non-development purposes.
The two demons communicate over USB by default, but can be told to communicate over Wi-Fi, or any other TCP/IP channel that is available.
The computer-side demons aren't identical, since they run on significantly different operating systems, but they provide the same facilities to the adb client program.
