Google has released a new help document that defines the metrics used on the Google Search Analytics report that webmasters can find within the Google Search Console.Specifically, it aims at defining three core metrics used in the report; impressions, position and clicks.
What is an impression?
A linking URL records an impression when it appears in a search result for a user. Whether or not, the link must actually be scrolled into view or otherwise visible depends on the type of search element that contains the link, as described later.
Aggregating data by site vs by page
If a single search element contains several links (as many do), impressions are counted by URL or by site, depending on your view in the Search Analytics report.
What is search result position?
The Google Search results page is composed of many search result elements. Search result elements include blue link sections, carousels, Knowledge Graph cards, and many other types of result features. A single search result element can include text, interactive features, and one or more links.
What is a click?
For most result types, any click that sends the user to a page outside of Google Search is counted as a click, and clicking a link that stays inside search results is not counted as a click.
Clicking a search result to an outside page, returning, then clicking the same link again counts as only one click. Clicking a different link counts as a click for each link clicked.