Apple polishing refers to flattering a person, usually in the hope of getting some special favor. Consider going to your boss or teacher with an apple as a gift (this used to be done for teachers), then polishing the apple for them. You would think from this picture (probably rightly) that such a person is trying to gain special favor. Another slang term for this is "sucking up to". A person that "sucks up to" the boss is usually held in low esteem.

it means buttering a person