This is a In Buddhist event occurring from the 13th to 16th of July or August to hold a memorial service to the spirits of ancestors. Because the spirits of the dead are said to return at this time, fires are lit at the entrances to homes so the spirits do not lose their way, and, in addition to lanterns being lit inside homes, the Buddhist home alters are tidied up and vegetables and fruit are set out as offerings. And when bon is over, the spirits are sent on their way. This is called the escorting of the spirits and fires to speed their seeing off are lit at entrances of homes and offerings are floated on rivers and the ocean.
Bon Festival : Wikipedia