VSys Live sites define how VSys Live works. You will have the built-in "default" site and can have any number of additional sites each with their own rules, appearances, news, etc. From the VSys Live panel click on VSys Live sites and settings.
VSys Live is licensed on a per-instance basis and each instance of VSys Live serves a single site. More than one instance may be used for a single site for performance and redundancy, but each instance can display only a single site.
You can't delete the default site from VSys Live, but you don't have to use it. The default site is always defined because it contains settings such as account lockouts which are used by all VSys Live sites.