An image can be either bootable or nonbootable. A bootable image is one that contains the startup code that the IPL can transfer control to.

A CD (or floppy, hard disk, or other storage media) from which a computer can be started up, because it contains all the operating system software the computer needs to run. A bootable CD contains a bootable image - a file which is an exact representation of a boot floppy or hard drive. Bootable CDs are usually made according to the El Torito standard.

A disc or other storage media which contains all the operating system software a computer needs in order to run.