Mercurial is a type of version control system that helps developers manage changes to their code over time. It allows multiple people to work on the same project without overwriting each other's work. By tracking changes, Mercurial makes it easy to revert to previous versions if something goes wrong, ensuring that the project remains organized and efficient. One of the key features of Mercurial is its speed and simplicity. It uses a distributed model, meaning every developer has a complete copy of the project history on their own computer. This makes it easier to collaborate and share code, similar to other systems like Git but with its own unique approach.