Undefined Concepts - Environment Variables, Environment

[juliebates]

Brief definitions would be helpful.

'Environment Variables' introduced as 'not a feature of a shell' --
a) would be helpful to have defining statement re: what environment variables ARE
b) organization and content of this section suggests that environment variables are paths (and only paths, as it looks as if the examples are all paths - LD_LIBRARY_PATH, PYTHONPATH). Is this true?
if not, contextual explanation would be helpful

'Environment' = computational environment? or something more specialized?
would be helpful to define term in a few words, also likely helpful to have Environment introduced before Environment Variables

I see it first under Possible Conflicts:
"It might happen that PATH points to one environment first, while LD_LIBRARY_PATH points to libraries from another environment...."