Open Question: On google Adsense, what does eCPM mean?

What does eCPM mean? On my reports page in AdSense, it says eCPM = $8.85, I have no idea what that means since I only have $00.30 in my account right now.
I’ve already visited the AdSense help center. I guess I just don’t really know what the $8.85 means. Is that how much I’ve made off of the CPM ads on my site?