A Tank is a heavily armoured vehicle that is made up of the hull, at least one turret, caterpillar tracks and a usually heavy gun. There were three types of tank used during WWI and WWII, and one which is still used. They are (respectively) light, medium, heavy, and main battle tank. Generally, any tank is a machine to behold. Usually carrying a 105mm or a 120mm cannon, they have formidable firepower. Also, caterpillar tracks make them all-terrain vehicles.
General combat vehicles.
Holding the line.
Main Battle Tank
These have an important role in today's battlefield.