This plugin allows you to use longer URLs (permalinks), by allowing much more characters in your titles and slug. The important is that this is done in a way that is future compatible with WordPress core updates.
There is a 200 characters limitation on WordPress core nowadays and this limit is raised to 3000 with the plugin.
Plugin is always extending the current WordPress core code – your long URLs will work even after WordPress core updates.
This plugin is really useful especially in non-latin slugs because of the required url escaping that increases the length of your permalinks a lot.