Recently I had cause to define a macro called
\marks. If I try something like
I get the error
! LaTeX Error: Command \marks already defined.
In LaTeX, if I do
\show\marks I get
> \marks=\marks, which I think means it's a TeX primitive, but if I execute the same show command in TeX, I get
> \marks=undefined. I can't find
\marks in any documentation that I have. What does it do?