ELB automatically distributes incoming application traffic across multiple targets, such as Amazon EC2 instances, containers, IP addresses, and Lambda functions.
A load balancer serves as the single point of contact for clients. The load balancer distributes incoming application traffic across multiple targets, such as EC2 instances, in multiple Availability Zones. This increases the availability of your application. You add one or more listeners to your load balancer.
Types of Load Balancer
Load Balancer Benefits
Load Balancer Errors
If load balancer stops working or timeouts, the classic load balancer will return 504 error.
Internet Facing ELB
Internal Load Balancer
AWS Load Balancer Developer Guide