These are the conector/or gate ways through which system communicates with external devices (I/O devices) like mouse, keyboard, monitor etc.
It is used to connect the monitor to your system. It is a 15 pins connecror.
PS/2 PORT (MOUSE & KEYBOARD)
PC has two PS/2 connectors where keyboard and mouse are attached they are offen colour coded. Blue/Purple-Keyboard, Green-Mouse.
These are nine pin connectors and support devices that required serial data transmission. Com1, Com2.
It is a 25 pin connector. This I/O port sends data in parallel format. It is primarily used for ptinter.
USB Port is used for atteching USB complient devices like Mouse, Keyboard or USB etc.
It is used to connect a computers network card to a cable modem or to the network.