Input Ports and Output Ports are "addressable" entities in the processor architecture that allow values to be read or written from or to them. In a single chip device that address decoding and "interfacing" is done internally so that the actual pins can be used as digital inputs, digital outputs, analog inputs, or analog outputs.
In a microprocessor you have to decode the address and route data to or from the processor. That is the purpose of interfacing.
Last question is weather you can connect a device like a 7-segment directly to a processor's pins. You can IF, the processor pins can supply sufficient current to light the segments. Some can, but most cannot.