API Gateway is a serverless API builder, typically used in conjunction with AWS Lambda, and which would be used to replace something like an Express REST API on Node. To read more about where API Gateway would fit into a serverless application architecture read my post here:
Pricing is outrageously reasonable as well. Once you get past the free tier you are only looking at $1 USD per million API calls.
Here is a quick preview of what your dashboard will look like inside Amazon API Gateway after you have logged into AWS and created/named your first API.
The API Keys section only exists to give outside developers or applications access to your API, just like you would get an API key to Google Maps or another service. If your application is the only one that will have access to this API you can ignore this section entirely. Which is what we are going to do for now.
Another easy one is the custom Domain Names section. This is where you assign a custom domain name to your API, such as api.myapp.com.
Forwarding incoming requests to another http endpoint, and on the other https endpoint you want to validate the request stems from your API gateway API. The certificates allow you to validate that the traffic is coming from a valid source.
Settings currently just lets you provide a CloudWatch ARN role so that you can monitor your API usage in CloudWatch.