An online forum might have different structures, some are oriented to have discussions: someone open a discussion, also refered as thread, and others make posts as part of that discussion. This might be one of the most common structures used for online forums.
Refers to smalk talk, inconsequential conversation, trivial commentary, stuff unrelated to the core of the question.
A question that that might need improvement might be closed, meaning that the can't get new answers until they are reopened.
The structure of Web Applications Stack Exchange is, there are posts called Question, each post could have one or more answers.
Question should include only the information necessary to describe a specific problem. It should be direct, concise, clear and complete.
Answers also should be a straight fuller explanation of how to solve the specific problem when that it's possible and in the other case why it can't be solved or why the web application can't be used to do the task.
Both questions and answers should not include additional stuff like greetings, salutions, signatures, meta commentary like how was the experience about writing the post.
Questions and answer should not incite to have opinated discussions rather than a solution to the problem, concrete guidance about the task to be done.
Questions might that need improvement might be closed. This is done with the intention to prevent that new answers be posted to a question that might change making the answers to fail to address what is asked once the question was improved. Questions that are off-topic might be closed, some off-topic questions might be migrated to other Stack Exchange sites if they look to be appropiate for target site.
A question closed that is on-topic might be reopend once the closing reasons are fixed.