The purpose of the Site link Item is to reference the site which already exists in the web.config. Site Link Items are created automatically once the module is installed. If more sites are added to web.config after the module installation, an administrator will have to create appropriate Site Link Items manually.
The order in which the sites stand under the Sites folder is important for the SiteResolver method. The Sortorder field is used to sort the Sites collection. The default order is the same as in the web.config file.
If the site exists in the web.config file but has no appropriate site link, its order is considered to be zero.
If the site name in web.config is changed, the name of the Site Link Item should be changed manually as well.