The festival of Holika Dahan is celebrated every year on the day of Phalgun Purnima as a symbol of the victory of good over evil. It is celebrated by burning Holika, an asuri (demoness). According to the tradition, people contribute a piece of wood or two for the Holika bonfire, and this represents Holika being consumed by the fire in which she tried to kill her nephew Prahlad , a devotee of God Vishnu and thus Holi gets its name.
The night before Holi, pyres are burnt in North India, Nepal and parts of South India in keeping with this tradition. The youth playfully steal all sorts of things and put them in Holika pyre.
In some parts of India the day is actually called Holika Dehan. There are other activities associated with the story of Prahlad, but the burning of Holika is the one that we can most directly associate with Holi. Fire burnt on the eve of Holi (Holika Dahan) symbolizes the burning of Holika. The story as a whole is testament to the power of devotion (bhakta) over the evil represented by King Hiranyakashyapu, as Prahlad never lost his faith.

May this festival burn all the negativity and cruelty from your life and bring positivity and a better understanding of life.