file_get_contents(includes_url( ‘/js/jquery/jquery.js’ )); not working

i figured it out, i had to change

$jq = file_get_contents(includes_url( '/js/jquery/jquery.js' ));

to

$jq = file_get_contents(ABSPATH . WPINC . '/js/jquery/jquery.js');

and it worked. can anyone explain why this works and the old one doesnt?

thanks!