Hey, You can actually just google Grafana and Prometheus. But since you've asked, here I go:
Every application or website or even an organization produces a lot of data. The emergence of data science has proved that finding patterns and connections amongst these data can give you a better insight into building the product/business better. Grafana is an open-source solution for running data analytics, pulling up metrics and cool customizable dashboards. Grafana connects with most of the databases.
Prometheus is a monitoring tool. It's an open-source tool is written mostly in Golang and partly on Ruby. It is funny Docker compatible.