The exact definitions in the New York Penal Code (ignoring cases where the victim is under age) are:
First degree - the rape involves forcible compulsion or the victim is incapable of consent because they are physically helpless.
Second degree - the victim is incapable of consent because they are mentally disabled or mentally incapacitated.
Third degree - the victim is incapable of consent, or the lack of consent is for some reason other than incapacity to consent.
I bet he gets 5 years and there'll be something that makes it suspended or some such thing
My understanding is that he will get 5-25 years for the more serious conviction. He cannot get a suspended sentence for that. The less serious conviction could be anything from probation (i.e. a suspended sentence) to 4 years. Lawyers in the US seem to think he will probably get around 10 years.
Note that he also faces charges in California which carry a sentence of up to 29 years.