Lyotard

He noted the term “grand narrative” in the book ‘The Postmodern Condition: A Report on Knowledge’.

He proposes what he calls an extreme simplification of the “postmodern” as an ‘incredulity* towards meta-narratives’.
(*incredulity–the state of being unwilling or unable to believe something)

He rejects “grand narratives” or universal “meta narratives”. An example is that he rejects the ideas that everything is knowable by science or that as history moves forward in time, humanity makes progress. He opposes universal political “solutions” such as communism and capitalism as well as the idea of absolute freedom.

He notes that no one seemed to agree on what, if anything, was real and everyone had their own perspective and story.

Metanarrative – a narrative about narratives of historical meaning, experience or knowledge

Baudrillard

He argues that today there is no such thing as reality.

He developed the idea of simulation and simulacra.

Simulacra are copies that depict things that either had no reality to begin with or that no longer have an original.
Simulation is the imitation of the operation of a real-world process or system over time.