Organization is similar to folder (from Windows) in that they are used to administer and sort objects of various types. In Safewhere*Identify, these objects are User, Group, Claim, Transformation, and Connection. Organization does not have their own page because it is administered from the lists of these object types. If you add an organization to one list, it will also turn up on the other lists.
By default, there will always be one root organization that cannot be deleted. If you are a member of the root organization (meaning that your user account is registered directly under this organization), then you will have access to all organizations in the system as well as objects in them. If you are a member of a child organization you will not be able to see the parent organization(s) and objects located in these. You can only see your own “branch” of the organizational hierarchy.