This template will provision a highly available base ArcGIS Enterprise deployment on two AWS instances plus one instance for a file server. A base ArcGIS Enterprise deployment includes Portal for ArcGIS, a GIS Server (used as the portal's hosting server), ArcGIS Data Store (which will create a relational and tile cache data store and you can optionally direct the template to create a spatiotemporal big data store), and ArcGIS Web Adaptor. It will set up an architecture as shown in the graphic below.
arcgis-WebGISha-123456789.us-east-1.elb.amazonaws.comthrough CNAME mapping.
See Troubleshoot AWS CloudFormation stack creation in the ArcGIS Enterprise on Amazon Web Services help if you run into problems.