Both can be described as black sticky stuff, used for sealing and waterproofing of various surfaces.

Tar however is seldom still used in the world due to its carcinogenic properties. It is poisonous and therefore banned in some countries.

Bitumen has very similar properties and is utilised in the same manner as Tar, but Bitumen is less dangerous. For this reason most countries allow the use of Bitumen above Tar.

Tar comes from coal, whereas Bitumen is a by-product of oil (the oil of course comes from coal).

Although we don't use Tar people wrongly still talk about Tarred Roads or Tarmac.