An inside local address is the NAT term that is used to describe the IP address assigned to a host on the inside network. It is usually a private IP address.

An inside global address is the registered IP address assigned by the ISP, which represents one or more inside local IP addresses externally.

An outside local address is the IP address of an external host as it appears to the internal network.

An outside global address is the IP address assigned to a host on the external network by the host owner. The address is allocated from a globally routable address space.

NAT enables companies to use one IP addressing scheme within their network but translate those IP addresses for external communication. Static NAT assigns a permanent one-to-one mapping of local addresses to global addresses. Dynamic NAT assigns address mappings by using a pool of available addresses. NAT overloading or Port Address Translation (PAT) reduces the number of global addresses required by allowing multiple local hosts to share a global address.