Art appreciation is the understanding of the timeless qualities that characterise all great art, and personally i feel is a subjective matter; what I find aesthetically pleasing may not apply to everyone else. There are many reasons why we value art; because it informs us, because of its expressive quality, and because of its artistic quality. In this case, the latter is being discussed, that good art is good because of aesthetic enjoyment of form, the balance and structure and proportion. Its argued that content is not important, just the formal qualities make it good art, for example Jackson Pollock, his work is based on lines and colours and is valued very highly, therefore content is irellevant.
However the view that art should be valued for its expressive qualities or catharsis as Aristotle called it; the emotional purging and cleansing. He believed people watched tragedies to make themselves emotional and upset but in a way happy, as they then have purged any negative emotion they had. If art was merely something that caused emotion it would be trivial, but the fact that art can convey something that is transcendent lies its value. However the argument that forms matters shows us that anything can trigger emotions such as pity or fear, without having to be art, but formal qualities are unique.
Many people value art becuase it can inform us, we value it if it is true to nature or to life. Platos imitation theory applies here, that all artists are merely copying the form so it can not be good art, but all perceptual experience involves interpretation, so there is nothing to copy. Great historical paintings can give us visual knowledge of certain points in time, but limitations with this is that anything can inform us without being art, a book can inform us but isn't art. This ability to inform us is not what make sus appreciate it but the artistic qualities it