OverDrive is a provider of the backend infrastructure for libraries to lend ebooks, magazines and audiobooks to their members. They also used to have apps for ebook readers, Android/Apple phones/tablets and even in the browser to access the same resources. But right now, they are migrating those folks on to their app named Libby and keeping the OverDrive brand focused on their backend infrastructure, which is being expanded to support schools for the reading needs of their students too.
I discovered OverDrive as an app first on my Kobo Nia ebook reader. This app allowed me to search and add my library and then borrow, read and return ebooks from my library. The Kobo app did not allow access to magazines though - which was disappointing since their app had a text reading mode for magazines (whose graphics cannot be handled by ebook readers).
The Android app still seems to exist, which I use on my phone and tablet, but it pushes me to install Libby for a better reading experience.