Olives writes about feeling overlooked and then, suddenly, feeling seen. The speaker begins with a run of short, bare words: unnoticed, invisible, lonely. Calling themselves the moon makes sense here, since the moon is something people can look at but often don't think about. The lines are so brief that the loneliness feels almost physical, like a held breath.
Then someone arrives and the speaker finally shines, finally belongs. The expected next step is that this person must be the sun, since the moon only glows by borrowed light. The poem refuses that easy answer. "No. He was the darkness." Only against a dark sky can the moon be seen at all. So he didn't give the speaker light; he gave them a background to stand out against, a space to be visible in.
The mood is quiet, tender and a little surprising. It's gratitude, but with an odd edge, because darkness usually suggests something threatening. The poem leaves that tension open, and the reader is left to decide how to feel about it.