Subversion, commonly referred to as SVN, is an open-source version control system. It is primarily used to manage and track changes in source code, documents, and other digital assets over time. SVN allows multiple users to collaborate on a project, ensuring that changes are recorded and conflicts can be resolved efficiently. Though SVN is more commonly associated with software development, it can also be effectively used in email marketing to manage and track changes in email templates, campaigns, and assets.