One of two standard USB connectors, the USB Type A connector (technically known as a “Standard A” connector) is wide and flat in appearance. Type A ports are found on most USB host devices, such as desktop and laptop computers. Type A plugs are found on one end of most USB cables, including those that are “hardwired” into devices such as computer keyboards, mice, and trackballs, as well as integrated into smaller devices such as USB thumb drives.
Four-pin USB Type A connections are used for USB 1.1 and USB 2.0. USB 3.0 uses a 9-pin form of Type A connection, which allows for faster data transfer. However, the pins in the USB 3.0 version are arranged in such a way that compatibility with 4-pin USB 1.1 and USB 2.0 connectors is ensured.