When you are working with users and groups in EPiServer CMS, you have the opportunity to select which providers should store and manage the groups and users. It is possible to use existing groups from Windows in EPiServer, if you so wish. From an administrative point of view, this can save you a great deal of work. You will also have the opportunity to create your own groups in a database, for example EPiServer CMS's own database. Which of these two services you can use or if you can use both is configured in web.config.
When you select Administer Groups in Admin mode, all groups will be shown irrespective of the manager in which they are stored. The manager that manages the group in question is shown to the right of the group name.