Simplify the following text for a Grade 10 native English-speaking person.
Original: Serfdom , indeed , was an institution that reflected a fairly common practice whereby great landlords were assured that others worked to feed them and were held down , legally and economically , while doing so .
Simplified: Serfdom was the system where great landlords could make sure other people worked to feed them and are forced , legally and economically , to keep doing that .