Avalokiteshvara Bodhisattva is the Bodhisattva Compassion. He took a vow to save all sentient beings from suffering and delayed his own buddhahood to accomplish this vow. He manifests himself in several forms - two arms, four arms, thousand eyes, thousand arms, eleven heads, etc. His boundless compassion and altruism inspire many devotees. Through prayers and practice to Chenrezig, we aspire to transform our negative qualities into selfless motivation to help others.
It is also said that the benefits attributed to reciting his mantra "Om Mani Padme Hung" are immeasurable.