What is the Hectare ?

Source: en.wikipedia.org

" The hectare is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm²), or 10,000 m², and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is about 0.405 hectare and one hectare contains about 2.47 acres. "