React is built around a component-based architecture, where the UI is divided into small, reusable pieces called components. Each component encapsulates its own structure, style, and behavior, making it easier to manage and maintain complex UIs. Components can be composed to create more complex interfaces, promoting reusability and consistency across the application. React uses a declarative approach to define UI components, meaning developers describe what the UI should look like for a given state, and React takes care of updating the DOM to match this description. This makes the code more predictable and easier to debug.