This is feedback from python#100737 (comment)

This matches the wording from the `os.path.join` docs better:
https://docs.python.org/3/library/os.path.html#os.path.join

In particular, the previous use of "anchor" was incorrect given the
pathlib definition of "anchor".

While matching wording, I noticed that the constructor section uses the
word "segment". This word does not appear elsewhere in the docs or code;
we already have "part" and "component" to refer to the same concept in the
pathlib context.

Co-authored-by: Barney Gale <barney.gale@gmail.com>

Co-authored-by: Barney Gale <barney.gale@gmail.com>