what is a openers and closed questions

Open question you can answer.
Closed questions cannot be answered.

Where u can give answerer some options to choose is called closed Q.. and when u give free hand to answerer to give answer is called Open.. in mostly of Q are open ended Questions// wrong section

Each question has a 4-day open period during which people can post .
A question is closed to additional when a best answer is selected or when it is put to a community vote.
Once a best answer is determined, an Open Question changes status and becomes a Resolved Question.