Dropbox is a cloud storage service that allows users to access and share files from any device with an Internet connection. The document discusses how to set up a Dropbox account and access files via the web or by downloading the Dropbox app. It also outlines some of the key uses and advantages of Dropbox, such as enabling real-time collaboration on documents between students and colleagues and eliminating delays from emailing files. Tagging files in Dropbox allows them to be easily searched and organized by keyword.