“If we shadows have offended“ who said this what does it mean?

This is Puck's famous monologue near the end of the play in Act 5 sc 1. Puck is directly addressing the audience. He apologises for any tension the play might have caused them and wishes only good things to come to people. In the wider context of life, Puck asks the audience to remember that it is never too late to make amends with each other after a trying time. Once woken from the sleep of anger or ego-driven confusion, it is possible to still mend what is broken.