An Application Load Balancer (ALB) is a networking tool that helps distribute incoming application traffic across multiple servers. This ensures that no single server becomes overwhelmed, improving the overall performance and reliability of applications. ALBs operate at the application layer (Layer 7) of the OSI model, allowing them to make intelligent routing decisions based on the content of the requests. ALBs can handle various types of traffic, including HTTP and HTTPS, and support advanced features like SSL termination and WebSocket connections. They are commonly used in cloud environments, such as those provided by Amazon Web Services and Microsoft Azure, to enhance scalability and fault tolerance.