From Conflict of Nations Wiki
This light infantry unit, predominately used to conquer enemy provinces and cities and defend friendly provinces and cities. Mainly defensive in nature, these units have the airlift feature available from the very start.
Armor supporting infantry, best suited for open or accessible terrain types. They will prove to be very helpful when accompanying armored units.
Heavy infantry that can disembark at any coastal province and is very effective at attacking fortified urban strongholds. Although weak in difficult terrain, these units do not require the province to have a harbor or pontoon to disembark.
Light airborne infantry using helicopters or VTOL aircraft to air-assault enemy positions. Receives Air-Assault bonus if attacking.
Specialised infantry trained for combat in difficult terrain, but still capable in open terrain types. With a nice range of starting capabilities, these forces are equipped for many scenarios and promise to put up a fight. Special Forces can not conquer provinces and turn them into your own, unlike all other infantry. They are only able to fight any units present in said province.
Cost effective defensive militia that can be mobilized quickly and without army bases. An important tradeoff to note is that this unit's starting hit-points depend on the morale of the city mobilizing them.