Pathauto is an awesome module, but there may be a time when, for one reason or another, don't want or don't need to use it.

custom_url_rewrite is a function (not a hook) available in Drupal which gives you an alternative to configuring custom paths and storing them in the database.

Since this is not a hook, it is suggested you put this in settings.php. You can convert the alias into the source, and vice versa.