React is a popular JavaScript library for building user interfaces, particularly single-page applications. Here are some of its key features:

1. Component-Based: React is all about components. You build small, reusable pieces (components) and compose them to create complex UIs. Each component has its own logic and controls its own rendering.

2. Declarative: In React, you describe what you want to achieve, and React will build the UI to match that state. This makes the code more readable and easier to debug.

3. Virtual DOM: React creates an in-memory data structure cache, which computes the changes made and then updates the browser. This allows a special feature called "diffing" that efficiently updates only the components that changed.

4. React Hooks: Introduced in React 16.8, hooks allow you to use state and other React features without writing a class. This leads to cleaner and more readable code.

5. JSX: JSX is a syntax extension for JavaScript that looks similar to HTML. It's used with React to describe what the UI should look like. JSX may remind you of a template language, but it comes with the full power of JavaScript.

6. Performance: React is known for its high performance. The core algorithm is extremely efficient, making complex updates and rendering fast and smooth
   

7. Unidirectional data flow: The data in a React app flows in a single direction, which makes it easier to understand how the application works.

8. React Native: With React Native, you can develop mobile apps in JavaScript that are truly native.

9. Context API: React's Context API allows you to share state and other data between components without passing props down manually at every level.

10. Error Boundaries: Error boundaries are React components that catch JavaScript errors anywhere in their child component tree, log those errors, and display a fallback UI instead of the component tree that crashed.