RE: doc string for face-attribute-relative-p doesn't help

[Drew Adams]

The Elisp manual (node Attribute Functions) suggests that
face-attribute-relative-p is more or less obsolete, but I don't find
anything in the manual that explains what is meant by "relative". What is
relative to what, and how are they related? This blurb on
face-attribute-relative-p is the most I found concerning "relative", but it
doesn't help me:

 "VALUE ... is ... relative (that is, if it modifies an underlying
  or inherited value of ATTRIBUTE)"

I don't follow this at all. I don't see any explanation of "underlying", for
example.

Can this stuff be clarified? I frankly can't make heads nor tails of it. I
see "relative" all over the place, but I haven't got a clue what is meant. I
suspect it might mean something like "indirect" here (not relative), but I
really am not sure what is meant.

A simple example should be able to illustrate the meaning. Just as (car
(cons x y)) = x shows what car means/does (for a cons), the doc should be
able to explain what is meant by "relative" by showing an example. This
shouldn't be that hard to communicate.