React is a JavaScript library that provides the building interactive user interfaces for web and mobile applications. It is a component-based frontend library produce only for the view layer of an application.

Note: In Model View Controller(MVC) architecture, React is a view layer that defines the looks and feels of application.

React applications is work on components that rendered some output. A component is a mixture of HTML and JavaScript that defines the logic to display the UI. A component might include multiple other components too. Basically we can say, we write the react components for creating a React application.

React allows you to create large web or mobile applications that can change data, without reloading the page/screen. That means can change any component on run-time without affecting the rest of the applications. React also allows you to create reusable components which easy to import anywhere.