Strictly speaking its for a user to literally ask a question in the correct category on something he/she genuinely wishes to know the answer to and cant obtain elsewhere. Other users are supposed to use their experience and knowledge to answer this question,and the asker picks the answer that has most helped them.
Regretfully its hardly ever like that. Most of the time its people off on a personal agenda against someone or a political party engages in a rant,and many who answer also rant.