Speaking to Pitchfork, Koenig said

With a song like “Stranger,” even the name of it compared to “Oxford Comma” or “Mansard Roof”—it’s inexpensive. No expensive words. I still always want there to be text and subtext and sub-subtext. But I can give you a pretty straightforward definition of what that song means: It’s about when you’re in a house and you hear other people having a good time and you don’t feel left out because you have a sense of belonging. That’s something you don’t always feel when you’re younger.

I could actually say that that song takes place in a house, the singer’s in a room, and not in the same room as the other people. It’s as simple as that.