According to this article on “https://medium.com/knowledgebase/what-is-request-impression-fill-rate-ctr-and-ecpm-c3d7db01e021” very helpful
I used to have a google adsense account which make some money daily for a good legitimate original contents website that have organic traffic.
Request
An ad request is counted whenever your site requests ads to be displayed. It is the number of ad units that requested ads. We report an ad request each time a request was sent, even if no ads were returned and backfill ads were displayed instead.
Impression
An impression is counted each time an ad loads on a site. If you refresh the page, even if the same ad loads, a new impression is counted.
For advertisers, impressions are important because they tell you how many eyes have seen a particular ad. You can calculate the reach of the ad based on how many times it was seen.
For publishers, impressions are important because in the CPM (Cost Per Mille) advertising model, you are paid for every 1000 impressions of an ad served on your site.
Fill rate
Fill Rate refers to the rate at which we were successfully able to serve ads on a given website. This is also sometimes called Sell Through Rate.
G&R works hard everyday to make your fill rate 100% by sign on more advertisers. We also making deals with international ad networks to serve “backfill ads” when our ad inventory is low.
CTR
Click Through Rate (CTR) is a way of measuring the success of an online advertising campaign for a particular website as well as the effectiveness of an email campaign by the number of users that clicked on a specific link.
CTR = (Clicks / Impressions) x 1000
A high Click Through Rate is one indicator of the success of an ad. If a lot of people are clicking, your ad is obviously engaging and noticeable. If one of the goals of your campaign is to drive traffic to your ad landing page, a high CTR = success.
eCPM
The acronym eCPM means ‘effective cost per mille’. It is the outcome of a calculation of the ad revenue generated by a banner or campagne, divided by the number of ad impressions of that banner or campaign expressed in units of 1,000. The ‘M’ for mille in the name comes from the Latin meaning 1,000.