Social hierarchy and Feudalism? Easy 10 points!?

I am doing my AP Euro summer ignment and i would like to know about social hierarchy of midieval europe. But the thing that i do not know is the difference between that and feudalism. They seem the same thing to me. My teacher said that Social hierarchy is like the pyramid and Feudalism is like the whole system. I am so confused i need help! Bad. Experts of history!