The CIR port is a IrDA- port with enhanced IR- transmit range.
A IrDA port is used for a infrared- communication between a Pocket PC and a smart phone or a PC (e.g. a ActiveSync connection instead of USB).
Most of the Notebooks have a IrDA- interface included. There exist also cheap (<$30) IR- to serial adapter for the PC (e.g. from Actisys).