You may have used ebooks from the library before. Here's a quick description of the differences between an ebook and a digital book. 

Digital Books

Digital books are created by your library from a physical book that we own. The library scans the book into PDF files, and makes the PDF copy available to view from OneSearch in the digital viewer. Digital books are not available for downloading or printing. Access to a digital book is usually limited to four hours at a time, but digital books may be renewed for longer if copies are available. The number of digital copies determines how many people can view a digital book at one time. Learn more about digital books from the Los Rios Libraries. 

Ebooks

Ebooks are purchased from vendors, who provide electronic access to a book.  Ebooks are usually viewed through a specific database provided by the vendor/publisher. You may browse the ebook options from the databases page or search for an ebook by title or topic through OneSearch. The options for accessing and using ebooks are decided by the vendor license that the library buys or subscribes to. This controls things such as how many people may use a book at one time, how many pages may be printed or downloaded, etc.