I'm not a saw marketing expert by any means, but this is how I understand it. A cabinet saw is generally floor standing, very heavy with cast iron and large table, belt driven, has an enclosed motor and mechanism, is often wired for 240V operation, and is more powerful than it's smaller brothers. They usually deliver better precision due to better fences and less vibration and cost in the thousands of dollars.
Portable saws like mine are smaller, direct drive, plastic housing with cast aluminum table, operate on 120V, and require a stand to operate standing up. They can (somewhat) easily be moved around with a weight of only 50-75 lbs. They can deliver a very good cut but not quite so fine as a cabinet saw, and prices range in the low-mid hundreds.
I think of a contractor's type saw as being a compromise between the two. They are floor standing saws that are lighter than cabinet saws, may have cast iron tables but those may be smaller than a cabinet saw, can be wired for 120V/240V, and are direct drive. The quality of cut is somewhere between that of a cabinet saw and a portable and they usually cost somewhere in the mid hundreds up to a thousand dollars.
Other features differentiate these saws as well, and price is a general indicator of quality and capability.