NAT or Network Address Translation translates private IPs to public IPs. Implemented to overcome IPv4 shortage.

Static NAT translates one private IP to one public IP at the IGW. Used to reserve a Public IP.

Dynamic NAT translates one private IP to the first available public IP. Used when public IPs are limited.

Static and dynamic NATs have a problem when there are (almost always) more private IPs than public IPs available for use.

PAT or Port Address Translation or Overloading translates many IP addresses to one public IP at the NATGW. Uses ports to identify individual devices. Used in home internet routers.

NAT Table keeps a record of private IP and private ports, and public IP and public ports so that the traffic from the internet can arrive the private devices successfully.