Gomez describes a stray dog that people in a neighborhood quietly look after. Folks toss it a scrap, leave water in a bowl, and that's enough to keep it from going feral. But the dog never moves in. It wanders through the edges of domestic life and takes what it likes without any wish to belong to anyone.
The speaker watches this with a mix of affection and humility. The key line, "That dog belongs / by not belonging," suggests the dog fits into the community precisely because it stays free. Then the poem turns. "That dog is not ours" sounds like a correction, but the last line flips it: "We are that dog's." The people thought they were the caretakers, yet the poem implies they are the ones who are claimed. The mood is relaxed and conversational at first ("You know / That one"), then quietly surprising, leaving a gentle sense that kindness and ownership aren't the same thing.