When the mind is focused on a neutral object, the mind is temporarily free from Panca Nivarana(which includes kama raga, and dosa). So the mind is suppressing these things on the one hand and focusing (concentration) on the other. This leads to the Jhanas( Anariya)
För Ariya, one already knows about Anicca, Anatta, Dukha and also the Asubha nature of the kama raga. So the object in this case would be Nibbana ( which is the relief one feels when such things are not present in the mind) . The ariya has experienced some “Cooling Down”, so he/she can recall that state of mind and focus on that. If the Ariya is an Anagami, then the Jhanas will be Ariya Jhanas as they are now permanent ( Anagami never craves for sensuality). This is my overall understanding.
