Citrix Netscaler IP addresses

Can someone explain the usage of Netscaler Virtual server IP address and the Mapped IP address ?
If I understand Netscaler appliance when it sits in the DMZ, it should have at least 2 Nics connected to External Firewall and 2 Nics connected to the internal firewall.
 So how do Netscaler Virtual server IP address and the Mapped IP address get used when the traffic comes in or goes out ?
Is Mapped IP the IP address of the interface of Netscaler facing the inside Network ?

Any explanation ?

Thanks