scs@eskimo.com (Steve Summit) writes:

The terms "upstream" and "downstream" are heavily used in much
writing about git, with obvious meanings and implications for
those who use git regularly, but they're not defined at
https://git-scm.com/docs/gitglossary .  Perhaps they should be?
(Sorry, I'm not nearly experienced enough with git yet to write
good definitions myself, though.)

Yup, 'upstream' has clear definition and we use the phrase a lot.
'downstream', not that much, primarily because your repository may
have its upstream (singular) but typically you may not even know the
set of people who consider your repository their upstream.

Having said that, there isn't much we can actually say about
'upstream' as a unversal truth, no?  I can readily think of this:

    Your upstream is the line(s) of history you base your
    development on.

but beyond that, there aren't much that is common across different
workflows how 'upstream' appears to you.  Sometimes you may ask your
changes to be pulled by it, sometimes you may directly push into it
while others like you who consider it their upstream do the same.

So...