CVS (Concurrent Versions System) is an open source version control system that enables developers to track changes to their code over time. It allows developers to work together on a project, store changes securely, and manage different versions of a project. CVS is a powerful, reliable, and easy to use tool which makes collaboration between developers a breeze. It also provides a great way to keep track of changes and allows developers to quickly revert back to a previous version of their code if needed. CVS is an invaluable resource for developers, and is an essential part of any development team.