A/C operation questions

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I've just recently bought a '99 Millenia S. The manual doesn't give a clear explanation of the A/C operation, so perhaps someone here could help.
When pressing the A/C button on the dash there are 3 positions:
1- A/C
2- A/C econ
3- A/C off (shows nothing on the dash display)
What is supposed to happen in the A/C econ setting? I gather that the A/C compressor is still engaged, but, how is it different from regular A/C operation in position #1?

Is the A/C loud enough that you can hear the A/C compressor cycling on and off? I know it's the wrong time of year, but, thus far I haven't been able to hear the compressor cycle and air coming out of the vents doesn't feel really cold, but, outside air has never been warm either.