ELB(Elastic Load Balancing)

Elastic Load Balancing automatically distributes incoming application traffic across multiple Amazon EC2 instances.
 
It enables you to achieve even greater fault tolerance in your applications, seamlessly providing the amount of load balancing capacity needed in response to incoming application traffic.

Elastic Load Balancing detects unhealthy instances within a pool and automatically reroutes traffic to healthy instances until the unhealthy instances have been restored.

Customers can enable Elastic Load Balancing within a single Availability Zone or across multiple zones for even more consistent application performance.