When people come to talk about monitoring, each one has his own understanding of what is Monitoring.
Not so often people know that there are different kinds of monitoring. We will try to give some definitions.
First, you have 2 main kinds of IT systems monitoring: performance monitoring and availability monitoring.
Performance monitoring tries to give an image of the ongoing performances of the system, while availability monitoring only tests if the system is accessible, whatever the performances are.
But within these 2 large categories, there are many kinds of monitoring, each giving more or less information on the monitored system.
The answer to availability monitoring questions is always yes or not while the answer to performance monitoring questions is a time measure or a percentage. Obvious?