A Load Balancer is a service that automatically distributes incoming traffic across multiple servers. This improves high availability, performance, and fault tolerance by preventing any single server from becoming overloaded.
In AWS, Elastic Load Balancer (ELB) routes traffic only to healthy Amazon EC2 instances using health checks. If one server fails, the load balancer automatically sends traffic to the remaining healthy servers.
In simple words, a Load Balancer shares traffic across multiple servers to keep applications fast, reliable, and always available.