Google Adsense

In the Google Adsense report there are seven columns.
Date Page impressions Clicks Page CTR Page eCPM [?] Earnings
What is the meaning of page impressions and clicks? When visitor view your page that is called page impressions.
when visitor click on ads that is called clicks?
1 ) Page Impressions: The number of times an ad unit (a collection of 1 to 4
ads). If you have two ad units on a page, then every time the page loads
you get two page impressions. Page Impressions DO include PSA (Public
Service Ads) and Alternate Ads.
2 ) Clicks: The number of times someone clicks on an ad. Clicks on PSA will
be included in this stat as well.
3 ) Earnings: Money you’ve made.
Derived Stats (Figures calculated from the real stats)
4 ) Clickthrough Rate: Clicks/Page Impressions. It is expressed as a
percentage.
5 ) Effective CPM:. Earnings per thousand page impressions. Calculated by
1000 X Earnings / Page Impressions
6 ) EPC: Your EPC is not displayed because it does not really matter. EPC
stands for Earnings Per Click (Earnings/Clicks) and is frequently talked
about.