PS "scratch drive"?

[Sfordphoto]

hey all,
i've heard scratch drive mentioned a few times here...what exactly is it?

[tim]

Google knows all (http://www.google.co.nz/search?q=photoshop+scratch&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a).

[S-S]

working disk space for photoshop while executing commands & rendering graphics... works best if not on same drive PS is installed on (assuming there is enough space on the drive)
scratch disk is cleared when PS is shut down/restarted (sometimes necessary during use if low disk space)