The first and most important Gutenberg dependency is React, a library building user interfaces. Facebook leads and oversees the development of React as part of its open source initiative.
React itself does not make any assumptions about what the rest of the application is build on. As a consequence, React apps can run in the browser and on the server. You can even power mobile apps with React.
ReactDOM is the React library to interact with the Document Object Model, or DOM. The DOM is the programming interface for HTML and XML documents. ReactDOM renders interfaces built in React inside of the browser.