A moderately unkind smart-ass thing to say to someone who says something that doesn't matter. Most people who say this are either in a bad mood, not a nice person altogether, or don't like the person they're talking to. It's not very clever, but alot of people thing it is.
High school kid in a MAGA hat smirks at a hostile Native American man who approached him and beat a drum in his face. The mainstream media uses newsplaining to tell Americans how racist the kid is.