Narasimha, the fourth incarnation of god Vishnu, is half-lion half-human. This incarnation  is to to alleviate the sufferings of devotees symbolizing fight against evil and tyranny. Lord Narayana is considered to be the origin of the other transcendental forms of God. From Narayana, Vasudeva is manifest, and from Vasudeva, Sankarsana is manifest (Agni-purana 48.13). And according to the scriptures, Lord Narasimha is an expansion (amsha) of Sankarsana.

Lord Narsimha Himself is recognized in the scriptures by a variety of forms,  distinguished by the arrangements of weapons in the hands, His different postures, or other subtle distinctions. Of these more than seventy-four forms,Nine are very prominent (Nava-narasimha):

(1) Ugra-narasimha or Ahobila Narasimha (in fierce form)
(2) Vira-narasimha
(3) Kopa-narasimha
(4) Kruddha-narasimha
(5) Vilamba-narasimha
(6) Yoga-narasimha (who blessed Lord Brahma)
(7) Aghora-narasimha
(8) Sudarsana-narasimha
(9) Lakshmi-narasimha  (Malola-narasimha or Prahlada-varada Narasimha
with Lakshmi on His lap and blessing Prahlad)

Ahovalam in Andhra Pradesh is the only place in India where all nine forms of Lord Narasimha, Nava Narasimha, are worshiped. Ahovalam is said to be the place where Lord Vishnu accepted the half-man, half-lion form of Lord Narasimha in order to defeat the demon Hiranyakasipu.