Component composition in React is a technique of building complex UI components by combining smaller independent components. This pattern enables developers to create reusable, modular, and maintainable components.

In other words, instead of creating a big component that does too many things, we can break it down into smaller, more manageable components, each with its own specific functionality. These smaller components can then be combined to create the desired UI.

For example, let's say we want to create a form with multiple input fields. We can break it down into smaller components such as InputField, SelectField, CheckboxField, etc. and then combine them to form the complete form. Each of these smaller components will have their own functionality and will be responsible for handling their own state and events.

Component composition not only helps in making our UI more modular and easier to understand but also makes it easier to test and maintain. It also promotes code reusability and reduces redundancy.

In conclusion, Component composition is a useful technique in React for creating complex UIs by building smaller, independent components that can be combined to form the final UI.