This check ensures that the endpoint_configuration.types attribute for aws_api_gateway_rest_api resources is set to "PRIVATE", rather than "REGIONAL" or "EDGE". By exposing API Gateway endpoints to the public internet (for example, with "REGIONAL"), sensitive services can be accessed or exploited by unauthorized parties. Setting the endpoint type to "PRIVATE" restricts access to only sources within your VPC, mitigating the risk of data exposure or malicious traffic.