In office and in places where we have multiple systems sharing the same internet connection single IP Internet Protocol is used for it assigned by the ISP Internet Service Provider.
But how is it possible to use single IP with multiple systems .
This can be done with the help of NAT . NAT converts the public IP into private IP as there can be multiple private IP so everyone has as IP . But when anyone send message it is being sent by single IP which is public.
NAT converts these private IP into public IP when we send message. And when any message comes for user it converts the public IP into the private IP.
NAT is mainly used to restrict the company or an organization using public IP upto a particular number just for the sake of security and economy front of view.
According to wikipedia.org:
To remap one IP address space into another we use Network address translation (NAT) process. This process modifies network address information in Internet Protocol (IP) datagram packet headers when they are still in transit within a traffic routing device.