A Live CD/DVD or USB flash drive contains a complete bootable computer operating system (OS). When you boot a computer from it, the OS loads into, and then runs from memory instead of a hard drive. This allows you to run an OS without installing it or making any changes to a computer's current configuration.
To create one, download an ISO file containing the OS you want to use, (such as Ubuntu
), then use something like ISO Recorder
to burn it to a CD/DVD or USB key.
Boot your computer from this disc/key and your computer will be running that OS instead of the one on its hard drive.