An application cluster refers to a group or collection of interconnected computer servers or nodes that work together to support and run a specific application or set of applications. It involves distributing the workload across multiple servers to improve performance, reliability, and scalability. Application clusters are designed to provide high availability, load balancing, and fault tolerance for the applications they host. They often utilize specialized software and networking infrastructure to manage and coordinate the resources and processes within the cluster. The goal of an application cluster is to enhance the overall performance and efficiency of the applications, ensuring optimal user experience and maximizing system uptime.