Service that manages and routes API requests between clients and backend services. Like a receptionist that directs visitors to the right department and handles basic requests.
Mobile apps send requests through an API Gateway which routes them to appropriate microservices and handles authentication.
All provide a managed front door for APIs: routing requests to backend services, enforcing authentication/authorization, applying policies (rate limits, quotas), and offering monitoring. Azure API Management is typically broader (full API lifecycle, developer portal, products/subscriptions), while AWS/GCP/OCI gateways are often used as lightweight managed gateways in front of microservices and serverless backends.