Almost like slaves, but with some more rights. You are bonded to a landowner, and have some work on his land, or whatever he is requiring. It is like being slave because you cannot break the bond, you must do it, you will be arrested if you leave. But it is different because you are paid somewhat, and have your own rights to land, property, protection.
It is for example, you cannot pay rent, you are in debt, you will starve, so you can make a deal with your landowner that you will stay, but be bonded to them, owe them the debt in another way. That was the situation of my parents, and as their child the debt would be passed on and on endlessly, and it is not that it is ever paid off.