React and React Native are frontend Javascript libraries created by facebook to improve the speed and consistency of building web and mobile clients. Creating a simple to use frontend API, React and React Native allow you to build UIs more quickly than every before. With a component driven methodology and conventions, React and React Native allow companies to re-use code not only across different applications but across devices (Android & IOS).
This is why companies like Airbnb, Facebook, Intuit, New York Times and many more have adopted these technologies. A transition to React and React Native helps companies of all sizes scale and grow faster than the competition by providing better products to their users.