From the Help & Support files on VISTA hard drive (might be on XP, too; I didn't check):

What is Bluetooth wireless technology?

Bluetooth technology uses radio transmissions to enable devices such as computers, printers, mice, or mobile phones to communicate wirelessly over a short distance. Some of the ways to use Bluetooth technology are:

• To transfer files between computers or between a computer and another device
  
• To print using a Bluetooth enabled wireless printer
  
• To use a Bluetooth enabled wireless keyboard or mouse
  
• To listen to music using Bluetooth enabled wireless headphones
  
• To synchronize a Bluetooth enabled personal digital assistant (PDA) to a computer or another device
  
• To create a wireless connection to the Internet with a Bluetooth enabled mobile phone or a modem server
  
• To join a Bluetooth personal area network (PAN)