Hanuman, together with Ganesha and Garuda, is one of the three major Hindu deities with animalistic physical features. He is loved all over India as the monkey-god who so faithfully served Rama, Vishnu's seventh avatar (incarnation), in his war against Ravana, the demon king. Hanuman is a major deity in North India where he is regarded as a propitiator against all evil. Temples to him have been erected all over that part of the country each small villages and towns having their own "Hanuman" shrine to keep the populace within the ambit of his able and benign prowess.
Myth has it that Hanuman was one of the many creatures the gods created to assist Vishnu in his incarnation as Rama. The monkey god is the son of Vayu, the wind god, and Anjana, an apsara who was turned into a monkey by a curse. Dasaratha, the king of Ayodhya, a kingdom in the north of India at that time, did not have a son and was advised by the holy men to perform a ceremony with which he would ask the gods to favor him with one. He did so, with great pomp and piety, and was bequeathed with a cake of divine origin that he was instructed to share among his three queens. He did so but his second queen, Kaikeyi, was allotted her share last and took affront at this late treatment. She threw the cake away and a crow flew away with. Kaikeya repented and later became the mother of Bharata, the second of the four sons which Dasaratha was blessed with as a result of the ceremony. His first son Rama, born of his first wife Kaushalla, is the seventh incarnation of Vishnu and the epic battle he conducted to rid the universe of Ravana, the tyrannous demon king of Lanka, is well-depicted in the Indian epic Ramayana. Dasaratha's youngest wife Sumitra, bore him the twins Lakshman and Satrughna. They were the youngest and Lakshman was inseparable from Rama, his eldest brother, and his devotion to his eldest brother throughout their strife against the demon-king is still considered as symbol of fraternal devotion in India.
Going back to the birth of Hanuman, it is found that the crow who stole the cake after Kaikeyi threw it away flew with it into the forest. There it came upon Anjana, in her cursed monkey form, performing worship. Vayu, the wind god, was also fortuitously there at that moment and, seeing the crow flying past with the piece of cake in its beak, he blew hard and a strong wind immediately swept the piece of cake out of the crow's beak and into Anjana's hands. Vayu went away but was immediately replaced by Shiva, who instructed Anjana to eat the cake. She did so and conceived Hanuman, who is thus considered to be the son of Vayu.
From when he was born Hanuman proved to be such a voracious eater that is mother was beyond herself feeding him. He even attempted to eat the sun, an attempt foiled by Indra, the king of the gods, who threw his thunderbolt at the tremendous baby to discourage him from devouring the only source of light to the earth. This created a slight commotion in the heavens with Vayu coming to the rescue of his son but the gods intervened and persuaded Indra to apologize to Vayu. Peace returned and the gormandizing baby was returned to the safe folds of his mother while Surya, the sun god, was spared a horrible fate.
Nevertheless, there was always enough foodstuff for Hanuman and he grew up to become a warrior of immense strength and agility. He could move, both run and fly, at the speed of the wind, an attribute bequeathed by his father. He could also change his size at will – he could become so tiny that he could get into any room through the keyhole and he could expand into such an enormous figure that he could carry a whole mountain on his back. These abilities stood in good stead in the war he assisted Rama in against Ravana.
Ravana, the evil demon king of Lanka, was such a terrible despot that people, gods and all other creatures of the three Hindu realms prayed to the gods to save them from him. After Rama grew to marriageable age he became betrothed to Sita, daughter of king Janak. Subsequently, Ravana, being the despot he was, was presented with a chance to get to Sita alone while her husband Rama was away on a hunt and he forced her to leave her husband's hut in the forest and go with him to his kingdom across the sea. When Rama came back from his hunt he was overcome with grief and immediately set out after the demon king.
Ravana was a devout worshiper of Shiva and that benevolent god had bequeathed him with immortality and such strength that none could defeat him in battle. Rama circumvented this by invoking Durgha, Shiva's powerful consort, at a time of the year she was not usually worshiped. She blessed him with such extra strength that he was finally able to defeat Ravana and cut off that demon king's ten heads one by one.
Hanuman played a pivotal role in the battle against Ravana, which Rama fought with the assistance of his ever-faithful brother, Hanuman and an army of monkeys, bears and other creatures affiliated to him. When none could dare cross the sea to Lanka and get news of Sita who was imprisoned there in the palace of Ravana, Hanuman changed size to such a huge creature that he flew across from the Indian mainland across the strait of water separating it from the island of Lanka. There he again assumed his normal size and stole into the gardens of the palace. Finding that Sita was imprisoned in a room he again changed size, assuming the stature of a fly this time, and entered the room through the keyhole. Though Sita was inconsolable and beside herself with grief at the misfortune that had befallen her he somehow managed to reassure her that her lord would soon attack Ravana's army of demons, defeat them and come across to Lanka to rescue her from a fate worse than death.
While stealing out of the palace grounds on his way back to the mainland and to Rama Hanuman was spotted by some palace attendants. Ravana's demon warriors chased after the monkey god and captured him. Ravana, with his evil turn of mind, decided to have some fun with the peculiar god with his red monkey face, golden body and long curling tail. Ravana told his attendants to tie the god up and set fire to his tail. So, while the entire set of demon spectators looked on in anticipation of Hanuman's imminent live immolation the attendants quickly set out to do what their king had ordered them to. Hanuman, sensing his tail on fire and desperate to go back to his lord with news of Sita, decided not to waste any more time in futile efforts and changed size again. He quickly started expanding to his huge form. His expanding body tore the ropes that bound him apart and he was soon free but he kept expanding and even the demon army around their king began to feel alarmed at the monkey god's enormous proportions. Their foreboding of ill proved correct for the by then gigantic monkey god began laying about him with his enormous hands and legs and demons started spewing around like matchsticks. The god's tail was still on fire and when he swished it this way and that the fire spread onto the city and soon Ravana's beloved Lankapuri (puri: city in Indian languages) was aflame. In the commotion that ensued Hanuman was able to escape, albeit with a burnt tail and mouth. That is why it is to this day that the monkey god's images in his temples all over India depict him with a blackened face and a blackened tip of his tail.
Hanuman returned to the mainland with news of Sita and subsequently was hugely successful in helping Rama defeat Ravana and get back his faithful wife. The monkey god also helped Rama get back his rightful heritage. He helped reinstate Rama to the throne of Ayodhya. Dasaratha was dead and Rama ruled now in his place, just and caring of his subjects. Hanuman remained with Rama to the last, serving intelligently and strongly, with love and devotion. Rama relinquished his mortal self and left for the heavens to return to his divine self as Vishnu.
The monkey god continues to roam the three realms, having being granted immortality, ready always to bless those who propitiate him in hope of succor from the evils of the world.