Hanuman is a partial incarnation of Lord Shiva, who was the divine companion of Lord Rama during the fight with the demon Ravan. He is one of the Chiranjeevi or immortals and an ardent devotee of Lord Ram. He is a brahmachari; a Celibate, a shapeshift, a Vanar or a monkey,and very innovative. He is known for his strength, cleverness, and intelligence. He is also a yogi, bestower of Nav(nine) Nidhi and Asht Siddhi as was blessed by Sita Mata. He is the healer of all diseases, pains, and sorrows. He is also known as the remover of all obstacles, the protector and the saviour. His devotion towards Lord Rama makes him potent and master of all forms of knowledge, slayer of demons, evils, and negative energies. He played a very important role in making Ram victorious in his war against Ravan and bringing Sita back that is why he is the one who can grant boons of victory to his devotees. He is considered as the epitome of devotion, dependability, and trustworthiness.
Hanuman Puja is dedicated to God Hanumana. Shri Hanumaan ji is known to be the incarnation of Lord Shiva. It is believed that when Lord Vishnu took birth, in the form of Ram to defeat, the greatest demon king Ravan, the other Gods also took incarnation as monkey and bears to help him. God Sheshnag and Lord Shiva incarnated as Lakshman and Hanuman respectively.
He was born on the full moon day (Purnima) of the month Chaitra on Tuesday. That is why, every year when Chaitra month’s full moon day arrives, his birth-day is celebrated, which is called shri Hanuman Jayanti and Tuesday is considered very auspicious day to worship Hanumanji.