They are allowed to cultivate certain tracts of land themselves, but they also have to work for their lord. So they might help plant crops and harvest crops in the lord's land as well. And they also give a percentage of everything that they grow or everything that they do to the actual lord. And if the lord needs to go into war, they might have to be soldiers in that war. You might be wondering, well, that sounds pretty bad. It sounds similar to being a slave. One of the key differences is that a serf actually can accumulate things on their own.