Kal means time, he is the avatar of Shiva and the lord of time, though Bhairava means terrible, in-fact he is the terrible killer of unbalanced five senses. Story was like: Brahma used to have five heads (five senses) and once he lost his senses and start playing some mischievous then to make him learn a lesson Kal-Bhairava beheaded one of Brahma heads, since then Brahma has only four heads. But this story is just symbolic, Kal-Bhairava is worshiped to keep one’s senses pure and clean, and to remove malefic effects.
“Om Bhairavaay Namah.”
“Om Hreem Mahabhairavaay Namah.”
“Om Bram Kaal Bhairavaay Phat.”
“Om Bram Bhairavaay Namah.”
“Hrim vatukaya apadudharanaya kuru kuru batukaya hrim.”
“Om Kaalakaalaaya Vidhmahey Kaalaatheethaaya dheemahi Thanno Kaala Bhairava Prachodhayaath.”