ADB Ports

ADB stands for Apple Desktop Bus. A bus is a system of hardware, software, and wiring that lets all the different parts of your computer communicate with each other. There are different kinds of buses, and the ADB is specifically for input devices. An input device includes those items you input information into the computer with, such as a keyboard, mouse, trackball, joystick, or drawing tablet.

This is what an ADB port looks like, and the symbol that identifies it.