What is the file xmlrpc.php and is it necessary?

I made the update to WP 5.2 when it was released, but I just noticed this file (xmlrpc.php) for the first time because, alphabetically, the file falls to the bottom of my root directory listing. But because the filename is not preceded by “wp-” I am wondering if the file was placed there by the WP update, or by some other means. I’m not fond of mysteries this way.

Is this a legitimate file, and is it part of the WordPress architecture or something else?