Books (also called "Notebooks") contain a series of notes, just like pages in a real notebook.
Books are best used for similar items that have a natural sequence or chronological order to them. For instance, the default database is created with a Daily Notes book which is design to be used with one or more pages for each day, in chronological order.
You might use books for any number of things, such as:
- Meeting minutes for a regular meeting
- To keep a journal or diary
- Keeping a log of experimental results
- Chapters in a book you are writing
Or really anything else that you would normally use a notebook or journal for.
Notes can be added to or removed from a Book via the Entry menu, which also contains other commands to customize the Book's apperance and otherwise modify it.