Dropbox is a file hosting service that offers cloud storage and file synchronization. It allows users to access and share files from any device with an internet connection. Dropbox uses a folder on each device that syncs files uploaded to the cloud so they are accessible from any device. Key features include sharing screenshots, adding comments to files, viewing files without extra software, editing Office files online for free, selective sync to save space, version history, security, finding shared files, and backup of photos. Dropbox is available on desktop and mobile devices through apps.