USB stands for Universal Serial Bus and is a type of external connection for a variety of devices, including portable music players, printers, keyboards and mice. This connection uses ports and hubs to connect devices.
The USB port is the jack into which you plug a USB cable's connector. Some devices, like flash drives, plug directly into the port.
Internal USB Hubs
The USB port on a computer connects to a "hub" inside the computer. This may only be a microchip on the motherboard. The hub's job is to take data coming in from multiple ports and to send that data to the correct destinations.
External USB Hubs
External USB hubs are external peripherals that contain multiple USB ports, allowing the user to plug in several USB devices. They connect to a computer's USB port with a USB cable.
Powered Vs. Unpowered Hubs
USB cables can transfer electricity as well as data; this can recharge devices. However, only a certain amount of electricity can go through a USB cable. Most external USB hubs come with an AC adapter so that the hub can power multiple devices.
Many computer monitors and some keyboards have multiple USB ports and can therefore act as hubs. This is useful, as the USB ports on the computer itself may not be within easy reach.