I fumbled in vi and briefly saw this at the bottom of the screen, just as I was hitting ESC:
Like it was ready for me to type an arbitrary
ed command over a range spanned by the marks
'>. What's it called? What's the keystroke? And is there additional magic to set
'> to convenient locations?
Apology. I did try searching google with "vim < > mark" and got inundated with html-related stuff. I did not try "vim :'<,'>", as I now realize I ought to have done. I did try
:h < and
:h > but not
:h '< nor
:h '> which would have led me to the answer.