My Shia fellows told me that it’s the birthday of their ghayab Imam Mahdi that is why they play with fire crackers and wear new dresses.
Baraat does not mean good. According to 9:1 Baraat means hatred. بَرَاءةٌ مِّنَ اللّهِ وَرَسُولِهِ إِلَى الَّذِينَ عَاهَدتُّم مِّنَ الْمُشْرِكِينَ
Baraatun mina Allahi warasoolihi ila allatheena AAahadtum mina almushrikeena****A (declaration) of immunity from Allah and His Messenger, to those of the Pagans with whom ye have contracted mutual alliances:-