Extract from Wikipedia. ........

A wheelbarrow is a small hand-propelled vehicle, usually with just one wheel, designed to be pushed and guided by a single person using two handles at the rear, or by a sail to push the ancient wheelbarrow by wind. The term "wheelbarrow" is made of two words: "wheel" and "barrow." "Barrow" is a derivation of the Old English "bearwe" which was a device used for carrying loads.

The wheelbarrow is designed to distribute the weight of its load between the wheel and the operator so enabling the convenient carriage of heavier and bulkier loads than would be possible were the weight carried entirely by the operator. As such it is a second-class lever. Traditional Chinese wheelbarrows, however, had a central wheel supporting the whole load. Use of wheelbarrows is common in the construction industry and in gardening. Typical capacity is approximately 100 liters (4 cubic feet) of material.

A two-wheel type is more stable on level ground, while the almost universal one-wheel type has better maneuverability in small spaces, on planks or when tilted ground would throw the load off balance. The use of one wheel also permits greater control of the deposition of the load on emptying.