A Google Cloud load balancer is not a single thing. It is made of many different components that all work together to provide regional or global load balancing to your applications.
What follows are some quick diagrams I have created to better understand how all of the components that make up the various Google Cloud load balancers work together.
Global Load Balancers
Google Cloud global load balancers operate at a global scale.
HTTP(S) Load Balancer
Ports supported: 80, 8080, 443
Read more about HTTP(S) Load Balancing Concepts.
TCP and SSL Proxy Load Balancer
Ports supported: 24, 443, 110, 143, 195, 443, 465, 587, 700, 993, 995, 1883, 5222
Read more about TCP Proxy Load Balancing Concepts.
Read more about SSL Proxy Load Balancing Concepts.
Regional Load Balancers
Google Cloud regional load balancers operate only within a particular Google Cloud region such as us-central1 or us-east1.
Network Load Balancer
Ports supported: All TCP and UDP ports.
Read more about Network Load Balancing Concepts.
If load balancing one to many virtual machines:
If load balancing to an instance group: