The terms Recovery disc (or Disk), Rescue Disk/Disc and Emergency Disk all refer to a capability to boot from an external device, possibly a thumb drive, that includes a self-running operating system: the ability to be a boot disk/Disc that runs independent of an internal hard drive that may be failing, or for some other reason is not the operating system to be run.

The focus of recovery or rescue is not to lose the data files on the hard drive; the focus of restore is to restore the operating system's functionality (and subsequently restore the contents of one's latest backups).

The rescue/recovery tool uses media containing a backup of the original factory condition or a favored condition of a computer as configured by an OEM (original equipment manufacturer) or an end-user. OEM supplied media are often restore tools shipped with computers to allow the user to reformat the hard drive and reinstall the operating system and pre-installed software as it was when it was shipped. Many modern systems have eliminated use of a physical recovery disc and instead store this software in a separate partition on the hard disk itself.

As an alternative to using media supplied with a system, it is possible to make one's own rescue/recovery disk. The Macintosh computer tool's name is Disk First Aid; on Windows systems there is a Create Disk function.

When a factory reset is done, user data is lost. The term "OEM recovery" refers to that type of "recovery." What is "recovered" is the original system. Hewlett-Packard, using the term System Recovery, describes it as destructive recovery. They even advise removing "extra hard drives" to prevent loss of this too.

Although non-destructive alternatives do exist, the standard OEM Systems Recovery of Microsoft Windows-based operating systems involves booting from a separate hard drive partition, CD-ROM, or DVD, reformatting the hard drive and then copying operating system and software files. After the recovery process is completed, configuration such as the Windows Out-Of-Box Experience wizard is first run (along with any other additional setup the computer may perform), as it was on the initial startup of the computer. Most recovery systems use specialized software, though Toshiba and Dell licensed Norton Ghost technology for their recovery systems at one point. As of Windows Vista, Dell uses a Windows Imaging Format based image on a partition along with a tool launched from the Windows Recovery Environment's command prompt.

Most modern PCs store their recovery (non-destructive) or restore (destructive) tool on a hard drive partition rather than on bundled CD-ROMs or DVDs. They're typically accessed by using a specific key combination during system startup. There's less cost to the OEM, but exposes the user to hard drive failure.

An application used to create recovery discs or flash drive is sometimes offered to allow a backup of the recovery data. Recovery CDs can also sometimes be ordered directly from the OEM. For some computers, they can also recreate the recovery partition. Other recovery systems, such as those included with recent Apple Macintosh models, permit users to download the recovery partition over an internet connection, enabling successful recovery even if the hard disk fails or is replaced.