PAT (Port Address Translation), also known as NAPT, as opposed to NAT (Network Address Translation), is the mapping of multiple internal addresses of a router to a single public address, but with different protocol port numbers corresponding to different internal addresses. This approach is commonly used for dial-up access to Internet networks.
PS: NAT Chinese full address translation, generally refers to the internal IP and internal global IP one-to-one correspondence
PAT Chinese full port translation, generally refers to the internal IP and internal global IP one-to-many correspondence