Elementor is a live page builder for WordPress. It means that whole process of writing and designing is done directly on the page with no need to press “Update” or go to preview mode. Free version of this WordPress plugin comes with 30 of the most useful widgets such as button, image carousel, tabs, accordion, alert etc. Pro/paid version comes with even more.
Elementor Page Builder can work with basically any WordPress theme that follows general WordPress guidelines. There are also lot of templates, both free and commercial, that you can customize to match your needs. To start from scratch, use Hello Elementor, a lightweight, plain-vanilla theme for this page builder. Keep in mind that this theme is specifically designed to work with Elementor Pro.
Envato, the company behind the ThemeForest marketplace, is also the author of free WordPress plugin called Envato Elements. This plugin offers hundreds Elementor templates for all website niches. Combination of those two plugins can be used to create awesome websites directly from your WordPress dashboard.
Both plugins are open source.