Who is called a serf?
Who is the serf, which is a very common form of status in Medieval Europe and Russia, and is a concept that is especially interesting to those who do historical research today?
Serf is the name given to the peasant who works on behalf of the landlord on the land allocated to him by inheritance in Medieval Europe. In this system, which was quite similar to the slavery system, serfs -unlike slaves- could not be sold. Although serfs generally worked on land allotted to them, they could sometimes be employed on land not allocated by the landlord (demesne). In addition, they could only use the mills belonging to their own landlords to grind the grain they reserved for themselves.
The most important difference between serfs and free peasants was the freedom to migrate. Serfs could not permanently leave their lands or villages without their master's permission. Apart from that, they had to get permission from their masters to marry, change jobs or transfer their property. They were tied to the land, and when the land changed hands, the serfs entered the service of the new master. They were often mistreated and had very limited rights before the law compared to their masters. The only way out of serfdom was to be set free or to escape.
https://www.worldhistory.org/Serf/