USB (universal Serial bus) is a high-speed serial bus. A USB port offers higher transfer rate than that of a serial port. We can connect input / output devices such as a keyboard, mic, mouse, speakers, printer, scanner, flash drives, portable hard disk etc. It allows three types data transfer: isochronous (Real time), interrupt based and bulk data transfer.
USB cable has 4 electronic wires, which includes power lines and data lines. Two out of 4 are used to supply / carry 5V electric power to peripherals. The rest two wires are used for transmitting data and commands. Famous USB ports versions are USB, USB 2.0, USB 3.0, microUSB type-B (mobile phones), USB type-C.