Infrared can be used to wirelessly connect the phone to various devices, for various purposes. It can connect the phone to a computer, so that the computer can use the phone to make a data connection (to the Internet, for example.) It can also be used to exchange information such as phone book entries with other phones. Finally, some phones can also use it to send information such as phone book entries and calendar events to Infrared-equipped printers.
Infrared is a line-of-sight wireless technology that uses a beam of invisible light to transmit information. This means that the infrared ports of both devices must be nearby and aimed at each other for a connection to succeed.