Virtual IP
A "Virtual IP" is an IP address (from the Virtual IP Subnets pool) which is assigned to the client when the IPsec VPN is established. All inbound traffic from the client comes from this address.

When this box is checked, such an IP will be assigned (the client must request such an IP) upon the establishment of a VPN. If it is not checked, then the client subnet will be defined by the 'Network' value.

Please refer to your EnGarde documentation for more information on this subject.