Describe the give and take relationship between a lord and a vassal. what was the ultimate goal of the landowning lord?

A vassal lived on lands owned by the nobels. This vassal and his family served in the army of the landowning lord as payment for the opportunity to live and work on the lord's land. The ultimate goal of the lord was to amass power. In time a noble was able to collect taxes and determine laws on those inhabiting his land.