Each Stack Exchange site has a Help Center page What topics can I ask about here? detailing the scope of the site in question.
Ours is still a default stub:
If your question is not specifically on-topic for $SiteName, it may be on topic for another Stack Exchange site. If no site currently exists that will accept your question, you may commit to or propose a new site at Area51, the place where new Stack Exchange communities are democratically created.
Seeing that we currently have 46 questions out of 578 that are either closed or on hold, I believe the site and community has now had some time to properly establish its scope.
What examples should we list as on- and off-topic, respectively?
One bullet point per answer, and specify on-topic or off-topic. Include a rationale or link to other meta posts discussing the matter if such exist. Vote to indicate which you feel should be included or not.