what does grave accent ` and aposrophe ' do in elisp regular expression?

Question

I use C-h v to check the doc about this variable org-agenda-file-regexp.

It says it is a variable defined in org.el. Its value is

"\\`[^.].*\\.org\\'"

What is the meaning of grave accent ` and aposrophe ' here?

Answer 1

Regexp-Backslash

\`

matches the empty string, but only at the beginning of the buffer or string being matched against.

\'

matches the empty string, but only at the end of the buffer or string being matched against.