USB hard drives make it easy to copy, transfer, or backup your files through a USB 2.0 interface on your computer. There are a variety of USB external hard drives, ranging in different weights and dimmensions. Some USB storage comes portable, meaning you can put it in your pocket or purse to take with you when on the go. It makes it easy then to back up or transfer files while traveling. Many of these USB hard drives are also equipped with additional interfaces, like FireWire or an eSata connection.