A tank locomotive or tank engine is a steam locomotive which carries its water in one or more on-board water tanks, instead of a more traditional tender. Most tank engines also have bunkers to hold fuel; in a tender-tank locomotive a tender holds some or all of the fuel, and may hold some water also.
LB&SCR J1 class
A typical side tank locomotive from 1897
An example with a tapered front and cut-out to give access to the valve gear
Large USA 2-8-2ST. Note the short tank, avoiding both firebox and smokebox
A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material to heat water in the locomotive's boiler to the point where it becomes gaseous and its volume increases 1,700 times. Functionally, it is a steam engine on wheels.
LNER Class A4 4468 Mallard is officially the fastest steam locomotive, reaching 126 mph (203 km/h) on 3 July 1938.
LNER Class A3 4472 Flying Scotsman was the first steam locomotive to officially reach 100 mph (160 km/h), on 30 November 1934.
The Salamanca locomotive
The Locomotion at Darlington Railway Centre and Museum