art, and its purpose?

basically what is the definition of art, and its purpose, and that of art galleries?
surely, not crowd pulling.
whether general connoisseur has ability to judge the value of a piece of art, and the ability to judge the depth reached of artist  and the mastery of the artist on the themes ?
how is the price fixed--a factor of demand and supply? or on the nuances expressed?
what is the context of exposure ?
can art be great if it offends?
whether artist knows his journey forward or got stuck or reached a dead end or missed the track or compromised??
artist has any social responsibility or can express as uninhibited?
artist works in an environ of real life or lives in his private universe?
clarity on the abve may be relevant to the artist and the connoisseur .