TortoiseSVN is a Windows client for Subversion version control. It provides features for importing and exporting files to a repository, checking out working copies, committing changes, updating working copies, and viewing project history. The document discusses TortoiseSVN's installation, basic version control concepts, repository creation and management, daily use features like committing and updating, and resolving conflicts. It is intended as a user guide for getting started with and using TortoiseSVN for source control management.