a cold air intake put the filter close to the ground to suck in the colder air from the ground..
A short ram is a small (Length wise) fairly straight tube with filter put right behind the driver side fog light. A short ram sucks in air from behind the fog light and rams air (couldnt think of better way to say) into throttle body..
Since ram air is more in engine bay area and closer to engine it can get warmer air coming form engine so HP from cold air may be a little higher.. but from my experience on the xb not really a noticable difference except sound and price..
but my knowledge comes from driving my xb with the Weapon*R Dragon Intake and someones with an AEM Cold air intake. but will say mine kinda works like a cold air also because the end of the tube where the filter goes angles down towards the ground behind the foglight and when you press the gas you can feel it sucking air from in front of the tire..
I think the cold air intake can also be in the engine bay too, what some people do is have it in the engine bay and put an enclosure around it to separate the air filter element from the engine. But I guess the traditional way to do it is to route it so that the air filter is close to the ground.
if you are referring to perrins "cold air" it really isnt cold air. where it routes back up and sits between the radiator and the intake manifold. its blowing lots of hot air.with an aftermarket vented grille it can be considered as a short ram, but i personally dont understand what is cainged from this being in such a hot area.