When a visitor takes the desired action while visiting your site, it is called conversion. This can be a purchase, membership signup, download or registration for newsletter.
This term is used to define the number of times a company’s ad will appear to its target audience. Impression could also be related to a website and the number of times the web page appear in total.
Example of how impressions work: 1 visitor could view 5 pages which would create 5 impressions. 2 visitors could view 5 pages which would generate 10 impressions.