Summary: eCPM values, say $5.00 will determine how much you will get paid per click.. CPM values, say $2.50 will determine how much you get paid per 1,000 impressions. Example: even if your CPM impressions is below 1,000 per day, say, you are getting only 500 CPM impressions, then you will get paid $1.25 for that 500 impressions, no need for any clicks whatsoever.
Well, what confused me was the say that CPM and eCPM are two different things. In fact, it is one thing but measured differently.