NSX Edge provides routing services and connectivity to networks that are external to the NSX-T deployment.
With NSX Edge, virtual machines or workloads that reside on the same host on different subnets can communicate with one another without having to traverse a traditional routing interface.
NSX Edge is required for establishing external connectivity from the NSX-T domain, through a Tier-0 router via BGP or static routing. Additionally, an NSX Edge must be deployed if you require network address translation (NAT) services at either the Tier-0 or Tier-1 logical routers.
The NSX Edge gateway connects isolated, stub networks to shared (uplink) networks by providing common gateway services such as NAT, and dynamic routing. Common deployments of NSX Edge include in the DMZ and multi-tenant Cloud environments where the NSX Edge creates virtual boundaries for each tenant.