According to the VMware NSX Documentation, this VPN type must be configured before enabling a L2VPN. L2VPN stands for Layer 2 VPN and is a feature that allows you to extend your layer 2 network across different sites using an IPSec tunnel. Route-based IPSec VPN is a VPN type that uses logical router ports to establish IPSec tunnels between sites.
https://docs.vmware.com/en/VMware-NSX/4.1/administration/GUID-86C8D6BB-F185-46DC-828C-
1E1876B854E8.html

Source NAT (SNAT) is used to translate the private IP address (172.16.101.11) of the NAT VM to a public IP address (80.80.80.1) as the packets leave the NAT-Segment network. SNAT changes the source IP of outbound packets, allowing private IP addresses within the internal network to be mapped to public IP addresses for communication with external networks.

L2 VPN is a feature of NSX that allows extending Layer 2 networks across different sites or clouds over an IPsec tunnel. L2 VPN has an advantage of enabling VM mobility with re-IP, which means that VMs can be moved from one site to another without changing their IP addresses or network configurations.
This is possible because L2 VPN allows both sites to use the same broadcast domain, which means that they share the same subnet and VLAN.

Network Introspection is a service insertion feature that allows third-party network security services to monitor and analyze the traffic between virtual machines. Network Introspection can be configured on the host pNIC or on the partner SVM, depending on the type of service and the deployment model. The host pNIC configuration is used for services that require traffic redirection from the physical network to the service virtual machine. The partner SVM configuration is used for services that require traffic redirection from the virtual network to the service virtual machine. Network Introspection cannot be configured on the Tier-0 or Tier-1 gateways, as they are not part of the data plane where the service insertion occurs. Network Introspection also cannot be configured on the edge node, as it is a logical construct that hosts the Tier-0 and Tier-1 gateways.
Reference: Distributed Service Insertion, NSX Securing "Anywhere" Part IV