What does `grep -n` option mean?

Question

When I use find-grep in Emacs, this command is appeared. find . -type f -exec grep -nH -e {} +

I searched -n option in man grep. Why is not there? And What does it means?

Answer 1

From man grep on my computer:

  -n, --line-number
        Prefix each line of output with the line number within its
        input file.