Closed questions (or "On hold" questions) cannot be answered, but can be edited to make them eligible for reopening. See What does it mean if a question is "closed" or "on hold"?
Close voting can be done via:
- The web site, sometimes aided by tools found here on Stack Apps.
- The official (i)phone apps.
- The API.
See also: [The Community user deleted my question! What gives?][3]