The difference of APM Monitor component

question 1 The difference between the "Process Monitor - WMI" and the "Process Monitor - SNMP"

As the name implies, processes are monitored either through WMI or SNMP. WMI is a Windows-only concept and for that reason, it provides a little more information like virtual memory for each process. The bottom line is that for Windows boxes, you'll probably want to use the Process Monitor - WMI and use Process Monitor - SNMP for everything else.

question 2 The difference of Monitor between service and process

As far as I understand, the only difference here is how you identify what to monitor.  For example, if you were to monitor the SolarWinds Network Performance Monitor:

• For a service monitor, you would use the Service Name, which be NetPerfMonService in this case.
• For a process monitor, you would use the name of the process itself, which is NetPerfMonService.exe.

question 3 The meaning of "Performance Counter Monitor"，or the "Performance Counter Monitor" by what means of monitoring

Any performance counter that you can monitor on the Windows server can be remotely monitored by NPM through RPC.

question 4 The meaning of “WMI Monitor”， or the "WMI Monitor" by what means of monitoring

Any performance counter that you can monitor on the Windows server can be remotely monitored by NPM but this time through WMI.

question 5 If a service is up，in fact this service can not be used, in this case the APM monitor this service is up or down?

I'm a little confused by the last question. Can you rephrase it?