Basecamp is a web-based project management tool that allows users to share projects with teams. It provides features like to-do lists, file sharing, messaging, and calendars. To use Basecamp, users sign up on the Basecamp website and can then create projects. For each project, users can add events, files, to-do lists, and messages to collaborate with team members and manage tasks. The tool is accessed through a web browser and stores all data online rather than on individual computers.