Ho ho ho.. wrong forum... moved it
What an IR port is? In fact, an IR port is nothing more than some kind of receiver that reacts on IR-light and relays the received signal. By coding a bitstring, different signals can be sent and received.
Remote control: you push "play" -> RC transmits 10110111 -> CD player goes on play
If there's one in your PC? I don't know. Usually it's in your devices list in the hardware manager of Windows, called Infrared ports.
If your PC isn't a laptop the chances you have such a port are quit small. If you don't have a OEM pc (Compaq, Dell etc) the chances are even smaller.
You can buy different kinds of IR ports: USB models, models that can be connected directly to the mainboard (most mainboards do have an IR connector), or even some vintage serial ones....