What is "high level" or "low level" or "functional"?

......what does it mean for one library to be more "high level" or "low
level" or "functional" than another? On what basis should we make such
comparisons? A pithy answer is given by Perlis:

A programming language is low level when its programs require attention
to the irrelevant.
Alan Perlis

But how should we decide what is relevant?

Within the functional programming community, there is a strong historical
connection between functional programming and formal modeling.
Many authors have expressed the view that functional programming languages
are "high level" because they allow programs to be written in terms of an
abstract conceptual model of the problem domain, without undue concern for
implementation details.

Of course, although functional languages can be used in this "high level"
way, this is neither a requirement nor a guarantee. It is very easy to write
programs and libraries in pure Haskell that are littered with implementation
details and bear little or no resemblance to any abstract conceptual model of
the problem they were written to solve

Source Genuinely Functional User Interfaces