startTransition is a React feature introduced in React 18 that allows you to mark updates as "transitions." These updates are considered non-urgent, meaning React will prioritize keeping the UI responsive by deferring these updates until more critical updates (like user input) are handled. This helps in improving the user experience by avoiding UI jank during more complex state updates, such as navigating between screens or rendering large lists. You can use startTransition to manage these less urgent updates without compromising performance.