Communicating changes and communicating learning too! Every few years I rewatch one of my favorite videos on code reviews: https://www.youtube.com/watch?v=PJjmw9TRB7s.

Asking questions on code reviews is one of the most powerful tools to learn more about a codebase, and fostering a culture where junior devs feel empowered to ask questions is one of the best ways to help junior devs succeed.