Constipation is a condition of the digestive system where an individual has hard feces that are difficult to expel. In most cases, this occurs because the colon has absorbed too much water from the food that is in the colon. The slower the food moves through the digestive tract, the more water the colon will absorb from it. Consequently, the feces become dry and hard. When this happens, emptying the bowels can become very painful.