Art is the result of a creative process from a given individual, and is meant to touch that within others which is immaterial, abstract, insubstantial, "etheric". You could call this, emotions, memories, thoughts, or maybe even the spiritual self.
Art is not only a painting, a sculpture, or a well designed building. It can be comedy. It can be creating computer games. It can be music. It can be writing a novel, or, perhaps, imagining a whole new universe in a fantasy setting.
Art is whenever an individual creates an original unique work through their personal creative process, thereby bringing to the world something the world has never seen, exploring new grounds, new concepts, new ideas, in the process. Sometimes this creative process lends and carries on from previous ideas, moreover there is always something new that can be explored.