What are Impressions?

[stevy]

Google released one document about how impressions are calculated- https://goo.gl/Ivr5At
Here at starting google told how they are calculating impression. I am having one doubt here in this line-
"Note that the visible link URL below the title is not a hyperlink and so it is not recorded as impression."

Can anyone help me to understand this.

 

[RH-Calvin]

The amount of impressions is the amount of times that an advertisement has been shown (through Google AdWords or other forms of PPC advertising) or a webpage has been listed on a SERP (Search Engine Results Page, in the case of search engine optimization).