What does 'he' exactly mean?
The Hawaiian word He just means a/an. It is not used in every situation where a/an is used in English. In fact it is not nearly as common at all as English a.
The answer was given as He is a student., She is a student. That was confusing. I thought the sentence said: He is a student, she is a student.
It can be either. 'o ia is gender neutral.
Is there a gender specificnword for he and she respectively in Hawaiian?
None whatsoever. The only way to specify would be to refer to the person with nouns like wahine or kāne.