The square metre is a unit of area and is an SI derived unit with the symbol m².
It was introduced in 1954 when the International System of Units was established and was derived directly from one of the original 6 base units - the metre (m).
It can be prefixed with any of the SI symbols that multiply it up or down such as km² (square kilometre) or µm2 (square micrometre). It is the most commonly used unit of area and is recognised all over the world.
The rood is a unit of area used in historic England with the symbol ro.
Its unit size is equal to 1/4 of an acre, 10,890 ft² or 1,012m². A rectangle equal to one furlong in length and one rod in width is one rood in area.
Its use was very important in surveying land because of the ease of conversion into acres from smaller sections of land.