Tortoise SVN is a subversion client that is implemented as a Microsoft Windows Explorer extension. It is used to maintain current and historical versions of files such as source code, web pages, and documentation.
Subversion keeps a running log of the changes that have been made to a site and the user who made the changes. This makes it easier to manage the site and pinpoint mistakes or unnecessary changes, and Tortoise gives you access to check out files and commit back changes to them.
Tortoise is similar to Dreamweaver in the fact that both programs use a local version of the site that is stored on your desktop. This local version is the template that you use to make changes and add files. The update command in Tortoise is similar to the put command in Dreamweaver in the sense that they take the changes you made on your local copy, and then apply them to the live version.