PID is the Process IDentification number
C:\>tasklist
Image Name PID Session Name Session# Mem Usage
========================= ====== ================ ======== ============
System Idle Process 0 Console 0 28 K
System 4 Console 0 240 K
smss.exe 776 Console 0 424 K
csrss.exe 1120 Console 0 4,300 K
winlogon.exe 1288 Console 0 2,960 K