Temporary
storage directory on the
Mac OS for to-be-deleted files.
Files can be moved in and out of the Trash, but they are not truly gone until "
Empty Trash..." is selected (and even then,
recovery is possible if the stuff's not overwritten).
As part of Apple's early 1980s attempts to replicate the physical desktop on a computer monitor, a trash can was added to the Macintosh GUI. According to Bruce Tognazzini, the Trash was more importantly seen by the Mac and Lisa teams as a "neat" feature that people would like. It's an excellent example of human interface, reducing a concept most people wouldn't really understand (identifying tracks and sectors for zero-overwrite) to a simple idea folks were already familiar with (getting rid of files).
On most Macs, the Trash sits in the lower-right of the desktop, overflowing with papers when full, and looking quite slender and stately when empty. The trash icon was given an overhaul with Mac OS 8; the System 7 Trash was 2-D in appearance and bulged to the point of nearly breaking when files were inside. In Mac OS X Public Beta the Trash gains the appearance of a wastebasket and moves into the Dock. It remains to be seen whether this location will carry through to the final release, or if the Trash will get a contextual menu command for emptying like its Mac OS 9 cousin.
More than ten years after the Trash was introduced, Microsoft included a presumably more eco-friendly Recycle Bin to Windows 9x. The comapny line is that the true function of Recycle Bin/Trash directories is more accurately depicted by a recycling container, but let's face it: the only reason Microsoft gave it the unwieldy and decidedly lame Recycle Bin handle is Apple's lawyers.
I used to ResEdit the System and turn my Trash into a Nuclear Waste container, complete with a *zap!* sound upon emptying, but that got old fast.