As the legend goes, more than 700 years ago Vaishno Devi a devotee of Lord Vishnu, used to pray to Lord Rama and had taken vow of celibacy. Bhairon Nath, a tantric (demon-God) tried to behold Her. Making use of his tantric powers, Bhairon Nath was able to see Her going towards the Trikuta mountains and gave chase. The Goddess felt thirsty at Banganga and shot an arrow into the earth from where water gushed out. Charan Paduka, marked by the imprints of Her feet, is the place where she rested. The Goddess then meditated in the cave at Adhkawari. It took Bhairon Nath nine months to locate Her, the reason why the cave is known as Garbh Joon. Mata Vaishno Devi blasted an opening at the other end of the cave with Her Trident when the demon-God located Her.
(continued at : http://www.matavaishnodevi.com/legend1.htm )