what is obon? お盆(obon)英語でどう説明しますか？

Japanese people go to grave to pray on every August. 

And it is called obon especially on 8/13,8/14,8/15.

Obon is the most important Buddhist festival in Japan. It takes place in August . It is a time when Buddhists remember people in their family who have died.

Some Buddhists believe that the spirits of people who have died come back to the family home for the three days of the festival.