Elastic Load Balancing (ELB) is an Amazon Web Services (AWS) service that distributes traffic to multiple targets, ensuring balanced workloads. Classic Load Balancers and Application Load Balancers are the two main types of ELBs, with differences in routing capabilities. Monitoring load balancer performance is crucial for maintaining application availability and responsiveness. Datadog can be integrated with AWS to view and collect ALB metrics, including host health checks, request counts, HTTP error codes, and target performance. By monitoring these metrics, users can diagnose issues, adjust resources, and improve overall application performance.