USB Cables are used to connect various types of peripherals to computers / Laptops etc. USB will allow the connection of Mice, Keyboards, Scanners, Printers, Gamepads, Digital Cameras, Mobile Phones, PDA's etc to 1 single Standardsized Socket.
The USB family include:
USB-A, USB-B, - the Standard type USB connections which can be found on Printers, Scanners etc
USB Mini A, USB Mini B, - Used on Digital Cameras, Camcorders, PDA's, Mobile Phones. Also used on gaming consoles (PS3 controllers)
USB Micro A, USB Micro B, - Used on mobile Phones.