As per the epic Ramayana, Hanuman, the mighty monkey god who aided Lord Rama in his expedition against evil forces, is one of the most popular gods of hinduism in the Sanatana Dharma Pantheon. Believed to be an avatar of Lord Shiva, Hanuman is worshipped as a symbol of agility, physical strength, perseverance and devotion. In times of trouble, it is a common faith among Hindus to chant the name of Hanuman or sing his hymn - "Hanuman Chalisa". Hanuman temples are amongst the most common public shrines found in India.
Hanuman is renowned for his courage, power and faithful, selfless service. When Rama was searching for the kidnapped Sita, he came across Sugreeva who was in hiding, with his army & Hanuman, from his brother Bali. Sugreeva sent Hanuman to meet Rama to explore the possibility of joining forces against his brother Bali. Thereafter, Bali was killed, Sugreeva got his kingdom back, but Hanuman was with Rama forever. Later, Hanuman flew across the ocean to locate Sita, whom he found imprisoned in the Ashoka Vatika in Lanka. He consoled Sita and set fire to Lanka, destroying many rakshasas. He served as the emissary of peace to Ravana's court. He assisted Rama in crossing the ocean by helping him build the Ram Sethu Bridge along with his vanar friends. During the war he flew to bring the Sanjeevni Mountain, full of medicinal herbs to revive Lakshman who had fallen. When the victorious Rama returned to Ayodhya & was crowned king, Hanuman continued to serve him, ever at his service.
When Rama offered him any boon that he cared to name, he asked to live for as long as men spoke of the deeds of Rama. Thus as per common folklore, Hanuman is considered Chiranjeevi (living eternally). He is very happy when he hears the Ram-namam. Hence repeating the Ram naam is the best way to get his blessings. Vinay Patrika of Tulsidas declares :
Wherever the glories of Sri Ram are being sung, there Lord Maruti, Who brought an end to the rakshasas, will be present. He will sit with his hands folded above his head, with his eyes welling up, as he hears the stories of the Lord. I bow down to thee!"
As per the dictums of Vedic Hindu Astrology, Hanuman is the only deity in Hindu religion, over whom Shani could not cast his spell. Shani could not overcome Hanuman and as such people worship Hanuman to get rid of malefic effects of Shani. Likewise, Hanuman is also worshiped for deliverance from the evil powers of various other lesser demons, negative forces/demi-gods and negative energies.
While Hanuman Chalisa remains one of the most important devotional songs of daily Pooja, the following Sloka (# 3) has been excerpted from Sundar Kand of Sri Ramcharit Manas of Tulsidas :
I bow to the son of the wind god, the beloved devotee of Sri Rama, the chief of the monkeys, the repository of all virtues, the foremost among the wise, a fire to consume the forest of the demon race, possessing a body shining as a mountain of gold and a home of immeasurable strength.