Short answers, pulled from the story.
Bhairava is derived from the Sanskrit word bhīru, meaning "fearsome," and the full name means "terribly fearsome form." The name is also interpreted as meaning one who destroys fear or one who stands entirely beyond it.
In Shaivism, Bhairava is a powerful manifestation, or avatar, of Shiva. In the Trika system of Kashmir Shaivism, he is identified as the Supreme Reality, synonymous with Para Brahman. He is worshipped across India, Nepal, Indonesia, Sri Lanka, and Japan.
According to the Shiva Purana, Bhairava was produced by Shiva from the region between his brows, created to punish Brahma for falsely claiming to have found the summit of an infinite pillar of light. His first act was to cut off the fifth of Brahma's five heads. A second account holds that Bhairava emerged from a lock of hair Shiva threw to correct Brahma's arrogance.
The Vijñāna Bhairava Tantra is a key text of the Trika system of Kashmir Shaivism, drawn as a chapter from the Rudrayamala Tantra, a Bhairava Agama. It is structured as a dialogue in which the goddess Bhairavi asks Bhairava to reveal the path to realization of the highest reality, and Bhairava responds with 112 Tantric meditation methods called centering techniques or Dharana.
In Tibetan Buddhism, Bhairava is worshipped under names including Vajrabhairava, Mahākāla, and Yamantaka, classified as yidams or tantric meditational deities. The Vajrabhairava tantras were said to have been revealed to a teacher named Lalitavajra in Oddiyana in the tenth century. In the Gelug school, Vajrabhairava is one of three central highest yoga tantra practices.
Bhairava Ashtami falls on the eighth day of Krishna paksha in the Margashirsha month of the Hindu calendar. It commemorates the day Kala Bhairava appeared on earth and is marked by special prayers and rituals.
Bhairava is depicted wearing twisted serpents as his earrings, bracelets, anklets, and sacred thread (yajnopavita). He wears a tiger skin and a ritual apron made of human bones, and his divine vehicle (vahana) is a dog, known in Sanskrit as shvana.