Grafana is a several platform open source analytics and interactive visualization application. It can provide charts, graphs, and alerts when connected to supported data sources.
RTView is an application that allows you to see the state of running Cardano nodes in real-time.
Guild LiveView (GLiveView) is a local monitoring tool to be used in addition to remote monitoring tools like Prometheus, Grafana, or IOG's RTView.
Prometheus is important to monitoring your node because it queries your node and collects data