System Status Defication in Maintenance Order

Hi,

I was looking at the IW39 report and System Status for most of the Orders were as

TECO NMAT PRC  SETC

or few as this:

CLSD GMCO NMAT PRC  SETC

I checked the Action Log of the CLSD orders and they were initially TECO , then Reset to Un-Teco and then CLSD.

Can someone please explain me the difference between thses two status a(TECO & CLSD) as I need to build a KPI on Maintenace Orders that have been closed (not CLSD), just close in the sense that all work done on it and Notificatiopn completed.

Thanks

Faisal