I've heard a lot about Postmodernist Art but never really knew what it was since, at art school, you don't learn a lot about art after the so called period known as 'Modern Art'.
In an attempt to remedy the situation I set about doing some research armed only with the most vaguest knowledge of my most favorite Post Modern artwork, which is of a modified road sign located in the United Kingdom that reads 'No God for the next 500m'. (I don't know what it means either. Some how it sounds plausible but is it?). I'm afraid I don't know the artist responsible for this gem of street sign 'tom foolery'.
It seems like this is the point of Post Modern Art. To take something familiar, change it into something that seems the same but isn't and then defy any kind of explanation.
In my research I came across Post Modernist essay generators and Post Modernist cartoon dialogue generators (that created captions for the same set of comic panels taken from several different news feeds). What both of these had in common was that their out put seemed to make sense and sounded plausible but when you really looked into them they made no real sense at all and were, in fact, meaningless nonsense. The essay generator in particular created very knowledgeable sounding essays - even citing notations and sources - but came with the disclaimer that the entire thing was meaningless and was essentially randomly generated.
So far as Post Modernist Art goes, my research reveals that it is often heavily influenced by the media and the repetitive nature of images. It is particularly influenced by Pop Art and Dadaism, sharing the fascination of the popular image in the former and the randomness of fate in the latter.
I haven't bothered to direct you towards examples of Post Modern Art. A simple Google search will point you in the right direction. Suffice to say, if Post Modern Art defies explanation then you can be comfortable in the knowledge that you're not meant to understand it either.