For our purposes we can call them 'glyphs' without much, if any, loss of generality.

Maybe he means "foo" and "bar", the canonical metasyntactic variables.

https://en.wikipedia.org/wiki/Metasyntactic_variable

I don't know either, but in English one definition/sense of para is "beyond", so it is "beyond language symbols", which shapes up to be something in the sense of a sort of programming paradigm where everything is subject to redefinition, particularly on the fly.