What is art and its function according to Freud ?

Sigmund Freud was a thought pioneer on a number of topics, but he was potentially most famous for his theories on psychoanalysis to treat patients with mental illness. He developed his own lexicon to express the notion that our subconscious contains unearthed and unacknowledged desires and memories. If these feelings and thoughts are volatile, they can fester and manifest in our normal behavior and feelings in the form of neuroses. Freud essentially tried to help his patients draw out any unresolved matters in their subconscious and consciously address them to cure them of their neuroses. 
Art is a way to transform intangible, unintelligible feelings into an observable, physical form. You may not be able to explicitly explain rage or unfulfilled desire, but you can perhaps sculpt or draw it. Freud viewed art as a means of sublimation, a socially acceptable means of releasing the tension caused by repressed feelings or memories in the subconscious. He even went so far as to speculate that creating art is a means of achieving sexual satisfaction. In Freud's view, the entire creative process was simply diverting repression into a form of beauty or entertainment, rather than letting it devolve into neurotic behavior.