Classic Load Balancer (CLB) is an AWS service that enables customers to balance incoming application or network traffic across multiple Amazon EC2 instances. CLB works by distributing the incoming traffic among all available EC2 instances, thus ensuring maximum availability and scalability for applications. CLB also provides various features such as health checks, sticky sessions, SSL termination, and connection draining. In addition to providing load balancing services, CLB can also be used as a proxy server for HTTP and HTTPS requests. As it is built on top of Amazon's robust cloud infrastructure, it ensures high performance and security for the customer's applications.