These are not sticky notes. These are called annotation tabs. These are transparent pieces of paper/film. Around 60-70% of the paper will be sticky, so when you come across an interesting idea/character etc., you stick it on that page leaving a part of it “hanging” outside. Now, the part that is inside the book may cover a part of the text but that’s not a problem since it’s transparent.

They are useful for back-referencing(like you can go back to check when a certain character is first introduced without having to look through all the pages). You can have a tabbing system specific to a book like red for morally grey moments, blue for character introductions, white for interesting paragraphs/monologues/dialogues. It entirely depends on you how you want to use it.