The word brahmacharini in Vedic texts means a female who pursues the sacred religious knowledge and also for a female who persuescelibation by controlling sexual desires. Worshipping Goddess brahmacharini on second day at sex chakra, after activation of kundalini at root chakra on first day, instructs us to follow celibacy.
She is the incarnation form of goddess Parvati when she did tapa for five thousand years with wish to marry Lord Shiva and followed celibacy and discipline. Rather it was the time that gods tricked lord Shiva to wish for marriage by kamdeva’s target arrow. Which symbolizes the downward flow of spiritual energy activated from crown chakra.
Mantras started from first day for siddhi or wish fulfilment should be continued everyday in each navratri. Mantras for second day worship of goddess brahmacharini are