GCP Backend services provide configuration information to the load balancer. Load balancers use the information in a backend service to direct incoming traffic to one or more attached backends. The backend consists of a pool of VMs and a health check that is used to verify that the VMs are operational.
gcloud compute health-checks create tcp test-health-chk \ --port 80
Created [https://www.googleapis.com/compute/v1/projects/*******/global/healthChecks/test-health-chk]. NAME PROTOCOL test-health-chk TCP
gcloud compute backend-services create test-int-lb \ --load-balancing-scheme internal \ --region us-central1 \ --health-checks test-health-chk \ --protocol tcp
Created [https://www.googleapis.com/compute/v1/projects/*******/regions/us-central1/backendServices/test-int-lb]. NAME BACKENDS PROTOCOL test-int-lb TCP