Ganglia is an open-source monitoring system designed to collect and analyze performance metrics from distributed systems. It provides a scalable and flexible framework for monitoring various resources, such as CPU usage, memory consumption, and network traffic, across multiple servers. The system uses a client-server architecture, where agents installed on monitored machines gather data and send it to a central monitoring server. Users can visualize this data through a web-based interface, making it easier to identify performance issues and optimize resource usage in real-time.