The Elementor Pro plugin is the PRO version of the free Elementor Page Builder plugin found in the WordPress repository.
Please note that Elementor Pro is an extension of Elementor. It means that Elementor Pro will not work if you do not install the free version of Elementor.
Here you can find addons of Elementor Page Builder that adds new elements/widgets to Elementor. You can also download the Jet plugins developed for Elementor from this page.