WPML (The WordPress Multilingual Plugin) refers to the WordPress plugin used to make WordPress sites available in multiple languages.
WordPress out-of-the-box does not support multilingualism.
WPML is compatible with other WordPress plugins and themes. The main function is to translate text in WordPress plugins and themes. Works with any plugin or theme that uses the WP API. It also allows you to launch a multilingual website. Use WPML to translate pages, articles, taxonomy and menus.