Though we posted questions to get some experts advice but unfortunately sometime it got closed or downvoted or put on hold. What makes the moderator or the users to take decisions on the post or answers that needs to be closed or put on hold?
As any stackexchange site is community driven, there's always some personal subjectivity involved. Thats why it takes 5 votes to close or reopen a question (excluding moderators).
The site has a few options to select from when closing questions, which generally relates well to the type of questiosn the stackexchange format is less suited for, or that are out of scope of a particular site.
Keep in mind that one of the goals of a stackexchange site isn't just to Q&A, but to collect the best answers to every question in a specific scope. That's why it's strongly recommended to reduce questions to their essence, remove irrelevant context, and categorize your questions as appropriate as possible. Closing all duplicates to any given question that is the same, will collect the best answers at a single location, and make the issue and answers to it a lot more discoverable through search engines. That implies you'll be able to help a lot more people in the future, than just the person asking the question right now.
At least, that is my personal interpretation of how and why the stackexchange format works so well. That does mean some questions are better asked in other communities (such as the salesforce developer boards or success community, both great resources and communities too).