Holika Dahan is a religious festival celebrated in parts of India, where people celebrate the triumph of good over evil.
Think of it like this - there's a very bad guy named Holika who wants to do bad things to people. But then a good guy named Prahlad prays to God and is saved from Holika's evil plans. In the end, Holika ends up getting burned, and Prahlad is safe, and everyone is happy.
So on this day, people celebrate by building a big fire (like a really big campfire), and throwing things like wood, leaves, and even old furniture into it. This is called the Holika Dahan bonfire.
People also sing and dance around the fire, while throwing colored powder and water at each other. This is called Holi and it's a lot of fun.
So, in short, Holika Dahan is a festival where people celebrate the victory of good over evil by lighting a big fire and having some fun.