A service that acts as a gateway to publish, secure, transform, and monitor APIs, regardless of where they are hosted (App Service, AKS, on-premises). It offers rate-limiting policies, caching, payload transformation, and a developer portal.
On AZ-305 this shows up as an API integration solution. Typical question: expose several different backend APIs as a single unified API with centralized throttling and authentication → API Management. It differs from Application Gateway in that APIM operates at the API contract level, not just HTTP load balancing.
Azure API Management (APIM) is a concept that can show up on the exam. Check the full guide to see it in context.