Charak Puja is a very enchanting folk festival of Southern Belt of Bangladesh and West Bengal. It is also known as "Nil Puja". The believers of Hindu religion celebrate this on the last day of Chaitra (Chaitra Songkranti). They believe that it will carry prosperity for them eliminating the sorrow and sufferings of the previous year. The festival is actually a festival to satisfy "Lord Shiva", the great "Debadideb" of Hindu Religion. Though the festival takes place on the mid night of Chaitra Songkranti, the preparation phase usually starts before one month of the day. The arrangement team of the festival go from village to village to procure the necessary components like paddy, oil, sugar, salt, honey, money etc. with the arranged and cosmetic Shiva, Parvati, Narod etc. The cosmetic Shiva is locally called "Nil Pagol" or "Jal Katha". On midnight of the Songkranti, the worshippers are gathered together to worship the God and after Puja the "Prosad" is distributed. Somewhere it is also known as "Hajrha Puja". The woman in this day don't take meal before Puja. Sometimes in this festival a human "Charak" is made ready to satisfy the Lord Shiva. The "Charak" is tied with a hook (Borshi) at his back and then he is moved round around a bar with a long rope. Though it is risky, they arrange it.
In Bangladesh it is frequently found to take place at Galachip Upzilla of Patuakhali District. Goalkhali, Gabua, Haridebpur, Lalua, Lohalia etc. villages are well known for "Charak Puja". Though the aristocracy and fluency of the festival is being deemed now, there are some who are arranging it every year with great devotion and dedication. It is a part of their life. May the festival be sustain long.

Source: Wikipedia