A Sensor is a small piece of code that instruments the monitored applications at certain points to extract relevant data. For example, a Sensor can transport tagging information from one host to another when a web service call executes. The AppMon installation includes a set of built-in Knowledge Sensor Packs for a wide set of application servers and frameworks. AppMon maintains these Knowledge Sensor Packs, and you can activate/deactivate them as needed.