A SharePoint Online site collection is a hierarchical group of sites that you, as an administrator of SharePoint Online, can manage on an individual basis or as a whole. The sites in a site collection share items such as administration settings, owner, and collection-wide permissions. Each sitecollection contains one top-level site that is created automatically when you create the site collection, and a number of subsites that are below it in the site hierarchy. Subsites can inherit permissions and
navigation from the parent site