The Bald Engineer also talks about current-limiting resistors. It’s a nice video, and I think you should watch it.
If there are things you don’t understand, you should write down some questions in your notebook, and come in prepared to ask them in class.
None. However, you are expected to have an understanding of how resistors work in a circuit (as exemplified in this video) as part of future writing assignments and examinations. Come to class prepared to ask questions.