OverDrive is a digital library that contains both ebooks and audiobooks. You can have 4 items checked out and 4 items on hold at the same time. There is no monthly limit for checkouts. Each item can be checked out for either 7 or 14 days, depending on your preferences. (Learn how to change your checkout period preferences here!)
You can use OverDrive on your computer or on most smartphones and tablets. It can be accessed through the OverDrive website or by using the OverDrive app or the Libby app. The Libby app has similar features to the OverDrive app, but looks a bit different. You can learn more about it here. You can also transfer OverDrive ebooks to most ereaders with a black & white screen.
OverDrive lets you sign up with only your library card number and library PIN/password. You’ll have the option to set up an OverDrive account with a separate username and password, but you don’t need to.
OverDrive has a great set of tutorials available on their website. They’re organized by device. You can view them here: https://help.overdrive.com/customer/en/portal/articles/1481729-getting-started-with-overdrive