This role-playing trope pretends that an animal, thing, or abstraction is a person, or that an absent person is in the room.
Ancient Greek and Roman educators considered personification an important part of school exercises. Students would mimic the voices of past historical figures in a practice called prosopopoeia. Personification lets you imitate another person, live or dead; or anthropomorphize (make human) an animal or object. The ancients talked to dead people all the time, moaning things like “Oh, Caesar, what you would think of us now?” They weren’t delusional; they were bringing in a free celebrity endorsement of their beliefs.
As with the other tropes, personification makes the world a richer place, where hermit crabs sing, dogs fly airplanes, brooms dance, and candles affect French accents.