Tar

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 (e.g. 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 component of the first sealed or tarmac roads.

For the computer term, see TAR file format.