What is the purpose of the usb port on the ps2?

May be...

I just want to know what it is for. Cause i have a movie on my usb and i plugged it in the ps2 thinking i could maybe watch a movie but nothing happened, but is it possible to do that

the usb is used for things like keyboards and headset in games like final fantasy XI you can communicate with other players with a keyboard. headsets are generally used for online games and games like socom there are also a couple of games that use the usb to plug in microphones and music peripherals