The Heart Sutra
The sutra deals with wisdom but not 'mundane or metaphysical' wisdom which causes one to attach to views, but rather 'transcendent wisdom', as Red Pine calls it. "Transcendental wisdom (prajna-paramita) is the wisdom that goes beyond anything 'earthly or sensory' yet leaving none of it behind, as Conze puts it. If it so transcendent, how can we even speak of it? Yet we must as 'we have no other means to lead beings from attachment toward understanding.' (Red PIne)
Who Avalokitsehvara actually was seems a bit hazy but Red Pine seems to think he was an actual person. Anyway, he is usually represented as a bodhisattva, one who forgoes their own enlightenment until they can secure the enlightenment of everyone else. He looks down and hears the suffering 'the cries of the world.'