Bookmarks are just links to certain pages of a book, you add or delete a bookmark, that’s all. Bookmarks are registered and saved in a list to later review.
Notes are also used as links to pages, but you can customize some text associated to it for later review.
Finally highlights are just marks on the text without listings, as you would do painting in a paper book.
You can select any text on the book at any momment, just make a long tap to select and let the contextual menu to appear. Move start and end marks to highlight desired text. On selection menu, select what you want to do with selected text.
Bookmark icon (the star one) will register the bookmark and highlight that text.
Reviewing notes and bookmarks of a book
In the main reading action bar select “Bookmarks“.
Choose the bookmark you want to go to or make a long tap for options.
The same happens with notes.