Tar is a naturally occurring black oily substance, which is a byproduct of
petroleum. It is very sticky and has a relatively low melting point. In some parts of the world, tar comes to the surface and forms
tar pits (eg. the
la Brea tar pits[?] in
Los Angeles). Before the development of inherently waterproof substitutes, tar was used as a roofant seal for
shingles, and also to seal the hulls of
ships and
boats and to waterproof
sails. It is also a vital componant of the first sealed or
tarmac roads.
For the computer term, see also TAR file format