Informations about Service Center > Environment Health > Process Instances

Hi all, 
I'm with some doubt. 

In Service Center in tab Envrionment Health on Process Instances Active, I had a high number of process active, but my doubt is exactly What is the Active process? Is it a thread for process or may a process open more threads. I mean, is this number exactly counting of process I'm processing or no?

Another doubt is, when I switch off my environment, those process keep alive in the applicatoin database waiting for process?