Dropbox is a free cloud-based file storage and synchronization service that allows users to access and share files from any device. Key features include 2GB of free storage, automatic syncing across all devices, easy file sharing capabilities, and a simple interface that requires no learning curve. The document provides step-by-step instructions for downloading and installing the Dropbox application on a computer, signing up for an account, accessing files via the desktop and online, sharing folders, and using the public folder to share links.