What are cloud monitoring systems?

Question

Monitoring

The goal is to find out what services you used, which ones you can advise, and paid ones are also suitable.
There are several companies that I administer, approximately 150 - 200 equipment (pc + server).
+ I would like to monitor the current network hardware.
I would like to receive statistics from the PC in memory, CPU load, on / off status, etc.
can be send a command to reboot (optional).
The goal is to learn exactly ready-made cloud services.