U3 : Computer Hardware Buyers’ Glossary
A technique for storing applications and their data on a USB (Universal Serial Bus)
flash drive. So for example you could take your mail program and your collection of
emails with you wherever you go. You just plug into any computer that is handy and
use it as if you were working on your home machine. Applications have to be
U3-compatible for this to work. They need to store all the configuration information
on the drive, not the registry.