Explain what Postmodernism means. How does it differ from Modernism and what are some of its characteristics and themes?

Modernism is very much from the print era with its
hierarchical, rational, centered, and scientific structure.  It's from the democratic
era of print in which authors used deductive theses to prove their claims.  It seems to
be mostly about ideas (abstract), presented in a cause-effect organizational plan.
 Also, modernism is based in Western (European/American mainly) values and culture
(again, mainly democracy and capitalism).

Postmodernism, by
contrast, is from the current mass media (TV, computer) era and, therefore, more random,
multicultural, subjective, and populist--in other words, there's no top-down
hierarchical structure.  Postmodernism wants to include all, namely feminist and
minority culture that have been excluded from the modernist past.  Also, postmodernism
largely rejects Western values and culture, looking at more diverse, complex, and
associative (not cause-effect) systems of organization, cultures, and
beliefs.

Good examples of these dichotomies can be found in
novels about war.  Whereas a modernist war novel may be a first-person point of view
which shows the horrors of war on a few individuals (through Western eyes), very much
like All Quiet on the Western Front (1929), a postmodernist war
novel like The Things They Carried (1990) switches narrative POV,
setting (time/place), and themes (non-Western) in order to show the chaos of war, as
well as the problems with memory and point-of-view. O'Brien very much focuses on the
roles of women ("Sweetheart of the Song Tra Bong") and the feelings of the Vietnamese
(enemy), even devoting a chapter to an unknown "Man I Killed."