Drain flies (they do look moth-like) are different in shape and size (larger) than these insect cousins, which are springtails. Fortunately, springtails don't hurt anything and only feed on debris like mold spores and pollen. Their presence might mean an area indoors is staying more damp than usual or might be molding if there is a water leak into wood or wallboard, but near a drain on hard surfaces they aren't necessarily an indicator of a problem.

Miri

This is awesome. Thanks very much for the explanation.

You're welcome!