What does ad impression mean?

Ads shown by Google on the web page visited by the visitor is called Ad Impression. When any visitor opens your content like blog or YouTube videos to watch or read, then Google Ad shows it. This is the Ad impression.

Sometimes these sites do not load due to slow or other reasons, then the ad impression is also reduced. Whereas the rate of clicks on this ad impression is called Impression CTR. At the same time, Earning per thousand impressions is called Impression RPM. Therefore, attention is paid to the fast loading of the site.