This is the top-level directory where home directories will be created. If your Virtualmin installation shares a server with many other services or standard system users, it may be useful to use something other than /home. The default is gathered from the Users and Groups Webmin module, which defaults to /home. The Users and Groups module allows for complex extensions to this convention, such as "/home/v/virtualmin", which can make directories easier to navigate if you have many domains on a single server. The Users and Groups module documentation in either of the Webmin books covers this feature in more detail.