A "port" is simply a hole in the sleeve of an engine. Usually, when people are talking about the number of ports an engine has, they are referring to the number of intake ports. For example, to be ROAR legal, a .12 engine can only have 3 intake ports and one ehaust port. There is also an outlaw class that will run motors with 5 intake ports and one exhaust port. This is only for .12 motors. When you get into the .21 size motors, they have even more ports. Hope this helps.