Attached is a picture from the CCNP SWITCH Foundation Learning Guide showing the Hierarchical Campus Model. You will not the redundant switches in each layer as well as links between them. Each switch block is shown in gray. Each switch block then represents a building, server farm, data center, the campus WAN, and service provider edge or the enterprise edge.
The enterprise edge is the area that contains all the connections to remote locations to include users, employees, the internet, partners, vendors, or other campuses.