Postmodernism is an era which follows modernism (post means after in latin). There is postmodern culture in every aspect of life: art, literature, philosophy, architecture, fiction, economics, etc. It's not only an art movement.One of the most well-known postmodernist concerns is "deconstruction." It means about that there is nothing besides what you see. There is no such thing as outside-the-text. What follows from that is that art (for example paintings) doesn't have to depict anything, since it's only art, only a painting, it represents itself, nothing from outside itself.
Alessandro Mendini uses a mixture of different cultures and different forms of expression. He has created graphics, furniture, interiors, paintings, and architectures. He is a big force in Postmoderism.
One could find information on Postmodernism in any Central Library at the sections Philosophy, History and Religion. One could also find information regarding Postmodernism online at Blatner, Philosophy Now and Wikipedia.
In the space of about 100 years, so called 'modern' art has gone from outcast to mainstream. There are many purposes for the arts in our society. One prominent example today is the use of 'modern' artistic innovations in the fields of advertising and business promotion. At the political level, the arts inspire new ideas and discussion. Modern art also serves to promote social interaction. In short, it is very beneficial