ELB, or Elastic Load Balancing, is a service AWS provides that automatically distributes incoming application traffic across multiple targets, such as EC2 instances, to ensure high availability and fault tolerance. ALB, or Application Load Balancer, is a specific type of ELB that operates at the OSI model's application layer (Layer 7), allowing for more advanced routing and traffic management features compared to the Classic Load Balancer and Network Load Balancer.