When I look at the ReHIPS log I see "PID" with a number shown in each entry. I assume that PID means Program ID, but what does the number mean?
PID is a Process ID. You can read more about it here https://en.wikipedia.org/wiki/Process_identifier In short words, it's a unique number assigned when a new process is started until it exits. So for example when you have multiple svchost.exe - s, by PID you can identify which one of them you need.
Thank you for the reference. I'll look it up.