Answer:
Medieval laborers were of the same class as peasants. Those who lived in towns and cities tended to be free, meaning free of manorial obligations, and those who lived in the countryside tended to be serfs, who had the manorial obligations. There were some slaves, but not very many, and the number declined as the Middle Ages passed.
The manorial obligations of the serfs consisted of contributions of labor, a part of the crop, or money, which was basically rent. In exchange for this they had a right to live and work on the manor and a right to be protected in times of trouble or famine. By contrast, those who were freemen had no such obligations, but also had no such security.