Dropbox is a file hosting service that allows users to store and share files across devices using cloud computing. It was founded in 2007 by Drew Houston and Arash Ferdowsi and has over 25 million users worldwide. Dropbox offers 2GB of free storage with options to purchase additional storage up to 100GB. It allows users to access and sync files across multiple devices and share files privately through links. Files are encrypted for security during transfers and storage on Dropbox servers.