I have two points. Is there a way to say "get the region between these two points as a string" ?

what package are you using to have two points?

(save-recursion .... some action ... (point))

sorry, maybe I should have used phrase "two locations" I only have 1 point

so I want the string between (save-recursion ... body ... (point)) and (point)

save-excursion

there's marker and point

which is probably what you want

in emacs slang called the region

(buffer-substring-no-properties (marker) (point))