Definition:
NATs are used to convert private (internal) IP addresses to unique external public (globally-assigned) IP addresses. That is, internal to the company, companies can use ANY IP they want to. The NAT changes the internal private IP address to a registered public IP address assigned by IANA and others. Private addressing can be used any network not connected to the public internet or networks that restrict private addressed being announced or advertised to the public internet. That is, private addresses are Network blocks or blocks of IP addresses used privately. In addition, NATs are used when applications sensitivity delay and end-to-end traceability (trace route) are not issues.