"Linux USB typically refers to the capability to boot and run
the Linux open source operating system from a USB flash memory
stick or USB pen drive. A portable Linux OS on a USB drive enables
users to easily take their operating system, supporting apps and
personal settings with them and run the OS from any computer that
can boot from a USB flash device. Linux USB can also refer to Linux
driver support for the three main USB standards, USB 1.1, USB 2.0
and USB 3.0."