Is this not when a Adwords Advertiser has selected your site to show blocks of 1000 impressions - which you get paid for regardless of clicks? Sorry I forget the official name for this, but the info is available in the FAQ's at Adsense.
 Hey look at that, I joined this forum the same day as you! but Im still a Junior and your a Senior.
if no clicks, probably cpm ads. i see them on my channels with little traffic. if i see lots of channels with 0 clicks and with 1 or 4 cent earnings, then i check to see if i am running cpm. it always is the case for me.