React is a popular JavaScript library for building user interfaces. It was developed by Facebook(Meta) and is often used for building single-page applications and mobile applications.

There are several reasons why React has become so popular:

Reusable components: React allows developers to create reusable components that can be used throughout an application. This makes it easier to build and maintain complex applications.

Virtual DOM: React uses a virtual DOM (Document Object Model) to improve performance by limiting the number of DOM manipulation operations required to update the view.

One-way data flow: React follows a unidirectional data flow model, which helps to prevent common issues such as cascading updates and makes it easier to reason about the state of an application.

Strong community: React has a strong and active community of developers who contribute to the development of the library and create third-party libraries and tools that can be used with React.
JSX: React uses JSX, which is a syntax extension for JavaScript that allows developers to write HTML-like code in their JavaScript files. This can make it easier to build and understand the structure of a React application.

Compatibility with other libraries: React can be used with a variety of other libraries and frameworks, making it a flexible choice for building web and mobile applications.

Popularity of JavaScript: React is built with JavaScript, which is a widely-used programming language, making it easier for developers who are familiar with JavaScript to learn and use React.

Performance: React's virtual DOM and one-way data flow model help to improve the performance of applications by minimizing the number of DOM manipulation operations required to update the view.

SEO-friendly: React applications can be made SEO-friendly by rendering the initial HTML on the server and then handling dynamic updates on the client side.

Large ecosystem: There is a large ecosystem of tools, libraries, and resources available for React, which makes it easier for developers to find solutions to common problems and to build and deploy applications.

Easy to learn: React has a small API and a straightforward syntax, which makes it relatively easy for developers to learn and use.

Strong documentation: React has comprehensive documentation that provides clear and detailed information about how to use the library and its various features.

Wide adoption: React is used by many large companies and organizations, which can help to build confidence in its stability and reliability.

Regular updates: React is actively maintained and developed by Facebook, and new versions and updates are released regularly, which helps to keep the library up-to-date and in line with modern best practices.

Versatility: React can be used to build a wide variety of applications, including web, mobile, and desktop applications, which makes it a versatile choice for developers.

Overall, React's combination of above points make it a popular choice for building modern web and mobile applications.