What does points on the back end mean in the movie industry?

i always hear that an actor or producer was paid "x" amount of dollars and he or she is getting "x" amount of points on the back end...like jack nicholson got 6 million of the movie and 6 points on the back end..what does it mean?
Update: i know it is a percentage at the end of the gross..but what is 5 points on the back end mean then?..say a movie makes 100 million..wat is five points on the back end
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