An API gateway acts as a centralized point for managing API requests in a microservices architecture. It serves several functions, including routing requests to the appropriate microservices, handling authentication and authorization, and providing features like load balancing and caching. The gateway simplifies client interactions by consolidating multiple service endpoints into a single endpoint. Additionally, it enhances security and allows for easier monitoring and analytics of API traffic. Overall, the API gateway is essential for simplifying communication, improving performance, and maintaining security across distributed services.