Nagios Core is an open-source monitoring system designed for infrastructure and network monitoring. The product monitors IT infrastructure components including servers, networks, applications, and services to detect and alert on operational issues. The system provides monitoring capabilities through a plugin-based architecture, with over 50 plugins available in the core package. These plugins enable monitoring of various infrastructure components and services across different platforms. Nagios Core supports customization through web interfaces, themes, and frontends that allow users to modify the appearance and functionality of the monitoring interface. The product includes support for both Windows and Linux environments, with mobile applications available for remote monitoring access. The monitoring system operates by checking the status of configured hosts and services, generating alerts when problems are detected. Users can configure monitoring parameters, thresholds, and notification settings to match their infrastructure requirements. As an open-source solution, Nagios Core is available for download and deployment without licensing costs. The product serves as a foundation for infrastructure monitoring, with extensibility through plugins and community-developed additions.