Hanuman was an ardent devotee of Shri Ram and Sita Mata. Hanuman was the Commander in Chief, of the army of King Sugriva - a Monkey King who befriended Shri Ram. He is said to have flown to Lanka to find Sita and help Rama win the war against Ravana. He was also instrumental in saving Lakshman's life during the war.
A: Anjaneya or the son of wind
N: Never got married, a celibate with utter respect for women
U: Undying devotion to Lord Ram
M: Maruti is yet another name
A: Agile with ability to conquer evil spirits as an "avtaar" of Lord Shiva
N: Names of the deity other than Hanuman are: Bajaranga Bali, Pavana Putra, Mahvira
On Hanuman Jayanti, celebrations are held at Hanuman temples all over India. Generally, verses from the "Hanuman Chalisa" are recited, wrestling games are held, idols are offered sindoor, paan, flowers and bananas. Some people observe a fast a day before and many others on the day of Hanuman Jayanti.
On Hanuman Jayanti , Hindus are advised to observe fast, meditate on Hanuman and Lord Rama, recite the Hanuman Chalisa and spend the day in recalling his qualities and asking his blessings.