Sati was the first wife of Lord Shiva. She was the daughter of Daksha who disapproved her marriage to Lord Shiva. in spite of his disapproval the marriage was done . On day he arranged a holy yaggya. He invited all deity except Lord shiva . Sati couldn’t bear such type of insult .
When she reached the place where the yagna was taking place she was ridiculed and insulted by her father by taunting on Lord Shiva.
She couldn’t afford such type of insult of her husband lord shiva and she threw herself into the fire of yaggya.
When Lord Shiva came to know about this ,he became angry into a rage and destroyed the yagna and killed Daksha. He opened his third eye and whole universe was going to destroy . His rage did not subside and he carried the dead body of Sati on his shoulders and destroyed everything in his path.
Lord Vishnu also tried an attempt to stop him used his discus to cut the dead body of Sati into pieces. These pieces of Sati fell in various places on earth and are now known as Shakti Peeth