With ArcGIS Enterprise, information can be shared as services published not only to ArcGIS Server, but also to ArcGIS Online and Portal for ArcGIS.
Publishing services
Publishing to ArcGIS Server
Publishing data and processes to ArcGIS Server is a common methodology employed by many organizations to share information. Publishing content to ArcGIS Server allows your services to be consumed internally within your organization and, if you choose, externally, either as public-facing unsecured services or secured services available through authentication.