Yes, too hard to explain quickly...
But here are some aspects of postmodernism you might want to research:
1. Rejection of Grand Narratives (basically, there are no truths- in itself a contradiction)
-The progressive emancipation of humanity (Utopia, heaven, paradise etc.)
-The triumph of science
2. Everything's relative (ha ha ha)
3. Deconstruction of texts (there's no 'real'/true/final answer or definition of something-> it can always be reworked and redefined)
4. Language is unreliable in construction of reality (our languages can never quite describe anything as it really is)
Following on from that, words don't tell us what something is; instead they eliminate some of the other words we might use to describe the object. Try imagining a cloud of words and one pushing the others down and away from it when you use it.
5. Death of the author: the belief that the reader/viewer's interpretation of a text is just as, if not more valuable than, the author's intention in creating the text.
6. Intertextuality: 'all texts are perpetually referring to other ones, rather than to any external reality' (Butler, 2002)
7. History and the writing of history--> just another narrative. Can't ever be truly objective and realist.
8. Discourse + authority
'language expresses the authority of those empowered to use it in a social group' (Michel Foucalt)
'The winners always write history', that kind of thing.
9. Our identities are not independent objects but instead are formed through discourse.
Yeah- postmodernism is really confusing- I'm only able to say this much because I was researching it just today and my brain is still struggling. Go borrow some books on it; try Christopher Butler's 2002 Postmodernism: A very short introduction, that's where I got most of this material.