They are two different networks. The first screenshot shows an isolated network configured with DHCP services.if you enable dhcp in an isolated network, an Edge device is being deployed with only the DHCP functionality.
The second screenshot shows an Edge Gateway which is normally used for Routed networks. this edge device can be configured for other services like NAT, Firewall, Static routing, etc.
Both of them provide DHCP services to vApps that connect to them. Note that there are 3 types of Organization vDC network: Isolated, Routed and Direct Connect