Datadog is a monitoring tool that allows users to collect, aggregate, and graph performance metrics from any part of their stack. It can be used to monitor anything, including custom data sources, websites, and applications. Datadog's powerful features enable the creation of custom dashboards and checks to measure server availability, latency, login availability, and other metrics. In this example, a team created a dashboard to monitor Pokémon GO's availability, using HTTP checks against Niantic's data endpoint to calculate server availability and latency, as well as logging in to the game every 30 seconds to measure login availability. This allows users to quickly check if the game is down or not, and provides a customized solution for monitoring infrastructure and applications.