This document defines and compares digital libraries and physical libraries. It explains that digital libraries store digital objects like text, images, audio and video in electronic formats that can be accessed locally or remotely. They use software to organize, store and retrieve these digital files. Some advantages of digital libraries are that they have no physical boundaries, are available 24/7, allow multiple access points, and aid in preservation of materials. However, challenges exist around equitable access, compatibility between systems, user authentication, information organization and interface design.