CPC means cost per click what that you get paid when someone clicks on your ad!
CTR means click through rate and it's a percentage that tell you how many clicks were made in relation to impressions.
RPM means revenue per thousand views Google estimates that your earnings will be X once you reach 1000 impressions it's based on CPC.
Impressions means views this how many times your ads were viewed. 1 impression = 1 view