A managed front door for a backend — API Gateway turns an HTTP request into a Lambda invocation, with no server of its own to run.
Amazon API Gateway is networking, not compute — it doesn't run your code, it sits in front of whatever does. A client sends an HTTP request; API Gateway receives it, decides which backend should handle it, and shapes whatever that backend returns back into a proper HTTP response. No servers to patch, no listener process to keep alive — the "front door" exists only while a request is actually passing through it.