Hey candidate,

As per your mentioned query, state category rank is that rank which you get among all the candidates of that category who appeared for the exam. While All India Rank (AIR) or Overall rank is the rank which you get among all the candidates who appeared for the exams.

Let us take a reference for making more understandable suppose you go for a admission and want admission in a XYZ (example) college , then of your AIR os enough to get seat in that college then you will get it from your AIR otherwise they check your state category rank then according to that they will decide whether you are eligible for the seat or not.

Basically , your category rank will help you to get best seat for you.

Hope you understand.

Thank you!!