Transfer of merit is when you do something nice, like doing good deeds or helping somebody else, and then the person who receives your help will also do something nice for somebody else. It's sort of like a domino effect - one good deed can help lots of people! For example, if you help your neighbor clean their yard, then they might help a friend move, who then might help another neighbor with cooking dinner. The original good deed you did kept transferring itself over to lots of other people, who then did something nice for someone else, and so on!