My meta question seemed to be deleted. Where can I find an explanation on deleting a question(on meta or main)? I would like to know on what conditions a question can be deleted. I searched help, meta, but I could not find it.
"I would like to know on what conditions a question can be deleted."
What happened in this case was that 3 users voted to delete it. You can read details on the technical ways a post can be deleted in general here (thanks quid for providing the link).
The technical mechanism applies regardless of what reason a user chooses to vote to delete a question. Perhaps a discussion on guidelines for when to delete questions could be useful, but before starting such I would recommend searching first for other meta posts on the matter (I have not done so).