A Software Load Balancer is a tool that distributes network traffic across multiple servers to ensure no single server becomes overwhelmed. By managing the flow of requests, it helps improve the performance and reliability of applications, making them more responsive to users. These load balancers can operate at different layers of the network, such as the Transport Layer or the Application Layer. They can also provide features like health checks, which monitor server performance, and failover capabilities, ensuring that if one server fails, traffic is redirected to others without interruption.