A spirit house is a place where people leave offerings to spirits. Spirits are things like fairies or ghosts that some people believe exist. The spirit house is usually a little house or box, and it is often put outside. People leave things like food, flowers, or other things that spirits might like. Some people believe that offering things to spirits will make them happy, and that the spirits might help them or protect them. It's kind of like leaving cookies out for Santa Claus on Christmas Eve, but for spirits instead!