Deriving from the Greek word for perception by means of the senses (aisthesis), and first used in the 18th century by the German philosopher Alexander Baumgarten, the term "aesthetics" (also known as asthetics or esthetics) refers to those principles governing the nature and appreciation of beauty, especially in visual art. Academically speaking, aesthetics refers to the branch of philosophy which deals with issues of beauty and artistic taste. [Quoted from:http://www.visual-arts-cork.com/definitions/aesthetics.htm].
As the subject is now understood, it consists of two parts: the philosophy of art, and the philosophy of the aesthetic experience and character of objects or phenomena that are not art. Non-art items include both artefacts that possess aspects susceptible of aesthetic appreciation, and phenomena that lack any traces of human design in virtue of being products of nature, not humanity. [Quoted from: http://www.rep.routledge.com/article/M046].