Simply Managing a Network through a protocol.
application layer
For network devices, in most cases yes. Operating systems do not need to rely on SNMP, and in the case of Microsoft, it's recommended against for security reasons.
SNMP is the most widely used protocol for network monitoring
SNMP
*HTTP*SNMP*Telnet
HTTP SNMP Telnet
Brute force
SNMP
SNMP
To use SNMP logs in Avid ISIS servers, you need to enable SNMP monitoring on the server. This will allow you to collect information such as system performance, errors, and alerts on network traffic. You can then use SNMP monitoring tools to analyze and track the data collected from the server's SNMP logs.
This link will tell you what you need to know: http://en.wikipedia.org/wiki/Net-SNMP
It's the backbone of network monitoring, but it's not the only thing that can or should be used. Microsoft for example does not recommend using SNMP for OS monitoring on security grounds. The more advanced monitoring software out there like NetCrunch 8 will use performance data from the OS itself, instead of relying on SNMP. Flow data like from NetFlow can also give you much deeper insight into your network traffic than SNMP can. Most simpler devices will rely on SNMP however, like your IP phones, printers, etc.