To understand Portal for ArcGIS, it’s helpful to examine how Esri server-based GIS products evolved. Years ago, Esri customers had to deploy ArcGIS Server onsite in order to publish web services. Eventually, ArcGIS Online was released with an interface that allowed people to publish feature services and (rasterized) tiled map services in the cloud without owning ArcGIS Server.
These ArcGIS Online hosted services were popular with customers that needed to make basic mashups with basemaps and thematic overlays but didn’t want to implement a full-blown ArcGIS Server. Other useful features included the ability to create, save, and share web maps using the map viewer tools you’ve been exercising in the past few lessons. This was done within the umbrella of an ArcGIS Online “organization” that Esri customers could create and administer.
In order to allow their customers the option to run such a solution on premises, Esri introduced Portal for ArcGIS. This gave organizations a basic browser-based interface where employees could upload data, make GIS web services, create maps, and share them with others at their workplace. It had the same features as an ArcGIS Online organization, but a connection to the Internet was not required.
This new Portal for ArcGIS product could be connected or “federated” to an ArcGIS Server site to give greater exposure to ArcGIS Server web services throughout the organization. The ArcGIS Server could further be configured as a “hosting server” in order to power the feature services and tiled map services published by portal users. Thus, the ArcGIS Online and ArcGIS Server functionalities were brought together. At version 10.5, Esri rebranded the ArcGIS Server + Portal for ArcGIS and their supporting components as ArcGIS Enterprise and developed a more integrated installation experience.
Esri now encourages customers to install Portal for ArcGIS as a user-friendly interface to their ArcGIS Server deployment. Think about the way you have been looking at your own ArcGIS Server site so far: because you are an administrator, you have access to ArcGIS Server Manager. That's easy enough to navigate, but your server users would just see the REST Services Directory, a very minimalist application that was built with developers (i.e., programmers) in mind. Portal for ArcGIS gives a nicer looking face to these services and can also function as a collaborative tool for internally sharing GIS services, maps, and data.
At this point, stop and read the following article very carefully, paying attention to the graphical figures. It describes in detail the different levels of integration you can configure between a portal and an ArcGIS Server site.
About using your portal with ArcGIS Server
When learning about Portal for ArcGIS, be aware that the term “portal” is a term broadly used across the web that can mean several different things. Even in GIS contexts, a portal is traditionally a site where a person can go to find data downloads. Indeed, Esri still makes available software called GeoportalServer for building these types of sites. Portal for ArcGIS, however, is broader than these traditional portals in the sense that people can publish items to a back-end server. They can also use interactive tools on the portal to make and share maps. In this way, the portal goes beyond being a data catalog to acting as a multi-purpose GIS platform.