"port" and "polish" are two different things that are usually done at the same time.
Due to mass production techniques, where the intake manifold bolts to the cylinder head for example, the intake ports dont quite line up evenly and there is some overlap. This restricts the flow of air into the engine, which reduces power output. "Porting" can be done on any metal to metal joins on the intake path, for example, intake manifold to cylinder heads, throttle body to intake manifold, supercharger to intake manifold, etc.
Porting refers basically to opening up the intake paths in these metal components by either cutting a larger hole in the metal or just enlarging it so there is no metal overlap to make more room for the air to flow through.
"Polish" is what it sounds like. It involves polishing the surface of the combustion chamber in the cylinder head so that it is smoother. This has the benefit of reducing hotspots, which discourages pinging, and also prevents the mixture, carbon deposits, etc from sticking to the head.