Final answer:
Serfs were the individuals tied to the land under the manorialism system, providing labor to the lord and the Church without being able to leave the manor without permission.
Step-by-step explanation:
The individuals who could not leave the manor without permission, yet were not slaves, and who would stay with the land even if it was sold to a new owner, were known as serfs. Serfs were obliged to work the lord's land and could not undertake certain activities like marrying or leaving the manor without the lord’s permission. Under the manorialism system, they were tied to the land, providing labor and goods to both the lord and the Catholic Church, which also owned significant land holdings.