Obon is an annual Japanese Buddhist celebration that commemorates ones ancestors. It is typically observed from August 13th - August 16th.
Traditionally, lanterns are hung in front of houses to guide spirits. Bon Odori (traditional Obon dances), food offerings, visiting graves, and alters at homes and temples are also common traditions people engage in during Obon. At the conclusion of Obon, floating lanterns are released into rivers and lakes to guide the spirits back to their world.
These traditions vary from region to region, but it is also common to see festivals across Japan during the observation of Obon.