A button on the
left side of your
keyboard. When you are
wordprocessing, it is mainly used to cause an indentation in the
text. Depending on your
software, it could create a constant-length space, or simply move your
cursor to the next
tab-index.
Also functions to move your cursor along the various tab stops of the current Windows application. Much confusion results when users attempt to cause an indentation while typing only to find that their cursor has disappeared into the ether.
Can also serve to bring up the automap in a lot of games.
It is also something I pried off of my keyboard and gave to my friend Tabitha.