AWS Elastic Load Balancing accepts incoming traffic from clients and routes requests to its registered targets Amazon EC2 instances, containers, IP addresses, and Lambda functions in a single or multiple Availability Zones. The load balancers monitor the health of registered targets and check for unhealthy targets. It stops routing traffic to unhealthy targets. It resumes routing traffic for that target only if the target is healthy.
If you are looking for an online course to learn AWS from industry experts, I recommend this AWS Training course by Intellipaat.
You can watch this video to understand more about how AWS elastic load balancer work: