In the context of a microcontroller chip, a "port" is simply a set of pins with input and/or output capability;

In the context of a PC, a "port" could be taken to include the connector, and any associated driver hardware and/or software;

In the context of the Internet Protocol (IP) a "port" number identifies a specific socket connection;

etc, etc...

A buffer is generally something that provides some sort of "protection" between two devices - like the traditional "buffers" on a train. Often a "buffer" will be used to provide increased drive capability and/or voltage tolerance, etc...

In software, a "buffer" is usually some sort of temporary storage where things are held whilst awaiting processing.

You need to be more specific if you want a specific answer!