Impressions
Impression is more or less a marketing term, normally calculated in bulk of 1000. It counts how many times a element (image, text, video) appears on a web page. If a advertisement network is paying $3/CPM (Cost Per Thousand Impressions), that means you are getting paid $3 when the banner appears 1000 times on your web page.
Clicks
Is how many times visitors visit your site.
Clickthrough rate (CTR)
A ratio showing how often people who see your ad end up clicking it. CTR can be used to gauge how well your keywords and ads are performing.
CPM
CPM stands for "cost per 1000 impressions." Advertisers running CPM ads set their desired price per 1000 ads served and pay each time their ad appears.
As a publisher, you'll earn revenue each time a CPM ad is served to your page and viewed by a user. CPM ads compete against cost per click (CPC) ads in our ad auction, and we'll display whichever ad is expected to earn more revenue for you.
Revenue
The revenue there is just showing your daily income.
On this particular day, sept 20th, 2013 you made $31.40 which is the highest on your screenshot.