CTR - Click-through rate is the ratio of users who click on a specific link to the number of total users who view a page, email, or advertisement. It is commonly used to measure the success of an online advertising campaign for a particular website as well as the effectiveness of email campaigns.
Impression - Sometimes called a view or an ad view, is a term that refers to the point in which an ad is viewed once by a visitor, or displayed once on a web page. The number of impressions of a particular advertisement is determined by the number of times the particular page is located and loaded.
Average position - How an ad typically ranks against other ads. See here.
The highest position is “1,” and there is no “bottom” position. An average position of 1-8 is generally on the first page of search results, 9-16 is generally on the second page, and so on. Average positions can be between two whole numbers. For example, an average position of “1.7” means that your ad usually appears in positions 1 or 2.
Your ad’s rank can change, causing its position on the page to fluctuate as well, so your average position can give you an idea of how often your ad beats other ads for position. However, the most important thing is to find what’s profitable for you, which might not be to show in the top position.
Average position may be less useful in optimizing for performance on the Google Display Network because of the diversity of websites on this network. If you want to measure performance on the Display Network, we recommend focusing on metrics such as conversions and ROI.
You can see an “Avg. Pos.” column for your ads, campaigns, and other elements, but average position is generally most useful to look at for your keywords. By seeing how your ad typically ranks when it’s triggered by one of your keywords, you can try to influence your position by changing the keyword’s bid.
Converted click - the number of clicks that convert within your chosen conversion window. So, if a customer makes two separate purchases after clicking on an ad, they will register as one Converted Click.
Conversions - Total Conversion Actions or Total Sales + Unique Leads. The new settings here give advertisers the flexibility to set the way conversion actions are counted by All or Unique.
View through conversion - is essentially triggered whenever a user is on the Display Network and sees your ad but does not click on it. The user later directly visits your website or finds it via an organic search or other referring site (basically any source other than Google / AdWords).
Display Network - businesses instead place display ads on a huge network of sites across the internet.
Search Network - When advertising on the Search Network, businesses place text ads in the search engine results.
Search Engine Markeing - SEM Involves promotion of websites by increasing visibility in search engine results pages (SERPs) prmarily through paid advertising.