React from Facebook has been around for over 7 years now and is the most common framework used on teams at Application Services.
React works by creating a virtual DOM model that the engine then uses to reshape the real DOM. The developer is able to create components using JSX to write HTML directly in JavaScript and create a hierarchy very similar to a real HTML document, but able to use JavaScript directly alongside the elements it will affect, listening for events, updating classes, text, and values.
Redux is often used alongside React to manage data and app state that needs to be accessed across multiple areas in the app, although it is not required and pertains more to applications that reach a certain level of complexity. There are also many alternatives to Redux, which we will be having a Community Meetup on shortly.
Some of the more recent features added to React include the Hooks API, which allows for the creation of functional components that can maintain state and references. For an overview of hooks, consider watching this PluralSight course.