A hectare is a unit of measurement of area. It is equal to 10,000 square metres, or a square with sides of 100 by 100 metres. 100 hectares is 1 square kilometre. Therefore, a farm with 200 hectares of fields has 2 square kilometres of fields.
The word hectare means 100 ares. Hecto is the metric prefix of 100. The are is a metric unit of area, equal to 100 square metres.