The term Cistercian is used to refer to an order of Roman Catholic monks. Officially the order is called Ordo Cisterciensis (OCist), or Sacer Ordo Cisterciensis (SOC). These people follow the same rules as the Benedictines, that is to say those of St Benedict. Over time, the Benedictines made some changes to the rules and the way of life.
The Cistercians reject these. They went back to what St Benedict had taught. Sometimes their rules were more strict than those St Benedict had given. They also went back to manual labour, especially work in the fields. Because of this, the Cistercians helped spread technologies around Medieval Europe. In 1882 certain monasteries formed a new order, called the Trappists. With time, they split completely from the Cistercians.