A serial port is a type of port which sends and receives data one bit at a time, as opposed to parallel ports which can send and receive in multiple streams. A COM port is a type of serial port. At...
Many modern laptops don't have a serial port at all. The most common serial ports on desktop computers were the old style of mouse ports that look like this picture: http://i32.tinypic.com/29vtir.jpg
A Serial port looks like this: http://www.ergocanada.com/ergo/tips/serial_port.jpg It is used to connect your PC to a monitor or projector. A USB port looks like this:...