"The Moths" refer to the little flying insects that come out of Abuelita's mouth after she dies at the end of the story. While still living, Abuelita told the narrator that the moths live in the soul and eat up the spirit, a process that perhaps results in death, though this is never made explicit. Either way, the moths are a part of us that keeps living after we're gone. The title, then, can be seen as a shout-out to not just Abuelita, but to the ways in which her legacy lives on after she dies. Deep stuff for a short story.