This is a celestial bodhisattva; the lotus he is holding in his proper left hand leads me to infer that it is Avalokiteshvara, the embodiment of compassion.

For Mahayana Buddhists, the bodhisattva is the ideal religious figure.  A bodhisattva voluntarily postpones his or her own nirvana in order to lead all living beings to enlightenment.  The bodhisattva path stresses altruism, compassion for others, and the effort to alleviate their suffering and ignorance however one is able.  It also demands incredible self-sacrifice (in effect, postponing one’s own nirvana forever), and taking the bodhisattva vow is seen as generating enormous religious merit.   

Avalokiteshvara is the embodiment of compassion (one of the fundamental Buddhist values), and is said to look down over the earth to respond to the needs of those who call his name with faith.  Given his power, it is not surprising that people began to worship him at an early date, one of his most famous images can be found at Ajanta.  A famous chapter in the Lotus Sutra (chapter 24) describes how calling on him can save one from various perils (fire, flood, storm, bandits, or execution), and bring blessings too.   

Although the bodhisattva path was an ideal for regular human beings,

Avalokiteshvara and the other "celestial" bodhisattvas have never been historical people (unlike the Buddha).  When Buddhism went to China, Avalokiteshvara become female, and as Kuan-yin (Japanese Kannon) is one of the most important Buddhist deities in popular piety.