Open Loop: Car is under wide open throttle or heavy throttle. This is when you want and Air/Fuel in the mid 11's to mid 12's. This is when the ECU ignores signal from the o2 sensors. Car is also in open loop when you start it up, until the o2 sensors heat up.

Closed Loop: Car is being driven under light throttle, just cruising around. This is when the ECU uses the O2 sensor signals to constantly adjust the Air/Fuel in order to reach stoich, 14.7 for gasoline.

I hope this helps clear things up. I intentionally avoided terms like tables, fuel trims, and scaling.