NSX Edge is a virtual machine or appliance and can be deployed by NSX Manager as OVF in that vCenter which is paired with NSX Manager.
When NSX Edge is deployed independently of NSX manager via a standalone mode and it is called as Standalone NSX Edge. This standalone EDGE is deployed by OVF which is obtained from NSX manager, and its initial configuration id done at time of deployment only.
The main purpose of the NSX Edge is to manage or handles the control and data plane and this NSX edge never communicates with NSX Controller.
Below figure demonstrate the logical view of the EDGE device which is doing routing between various virtual and physical network. The Edge when is placed between border of physical and virtual network is called as Perimeter Edge and the VLAN that connect between physical network and virtual network is called as Edge VLAN.