Let P be the power set of {a,b,c} Define a function from P to the set of integers as follows: $f(A)=|A|.(|A|$ is the cardinality of A.) Is f injective? Prove or disprove. Is f surjective? Prove or disprove.

I'm having a hard time understanding what this question is asking (as I have with most discrete math problems). What does it mean by "Let P be the power set of..."?

I'm having a hard time understanding what this question is asking (as I have with most discrete math problems). What does it mean by "Let P be the power set of..."?