Basically what this means is that when you login and view a book on line you can make notes on any part of the text, and also highlight the text different colours. This should be a real help to those you read books online and use it a study resource, and it is really easy to use.
CCEL give the following guidance on making an annotation:
“To make an annotation, go to a book page and highlight some text with your mouse. Then click one of the highlighter icons on the toolbar at the bottom left of the screen. There are three different highlighter colors, a button to add a note, and a button to remove any highlights in the selected region. After clicking one of the buttons your highlight should immediately appear on the page, or if you are creating a note, a text box should appear for you to type a note.”