Final answer:
Subversion (SVN) is a centralized version control system used to manage and track changes to files and directories, facilitating collaboration among multiple users on a project.
Step-by-step explanation:
The main functionality of the Subversion option when setting up version control for a new site is to manage and track changes to files and directories over time. This system, often abbreviated as SVN, is a centralized system that allows multiple users to collaborate on a project, each one working on their own copy of the files and then merging their updates back to the central repository. Subversion keeps track of every modification made to files and directories, and this history allows you to retrieve older versions of your data or examine the history of how your data changed.