It is very important for advertisers to understand the difference between a keyword’s search volume, and the impression number provided on reports.
When viewing reports, a search term’s impressions represent the total number of users who actually visited a page that an ad appeared on when a search was performed for that term. Therefore, according to Google, if an ad appears on the third page of search results and the user does not get past the first page of results, it does not count as an impression for the term searched for.
In contrast, a term’s search volume indicates the approximate number of times a term was searched for over a specific time period. Google recently made this valuable data available for searches that were performed at Google and its search network. This resource can be incredibly useful when developing and managing PPC advertising accounts.
It is important to understand the distinction between these two numbers. When viewing reports, advertisers might view a term’s impressions and mistakenly think that term does not receive much traffic, when in reality the term may receive plenty of traffic, but nobody is finding their ad because the positioning is too low. It’s certainly something to beware of.