Since I have a lot of problems using the same terms for the same things consistently, here a shortlist of what is named what. Don’t hesitate to remind me in case I use something wrong or invent something new that already has a term.

ad impression

Ad impressions are a measurement of loaded ads that are getting displayed by the user browser. Their number can be affected by ad-blockers and bots.

ad type(s)

Ad types define the kind of an ad, e.g. a content ad type has a text editor field, but no other options

ad unit

An ad unit is the ad you create with with Advanced Ads.

display condition

A condition about when and where to display an ad in the frontend.

Page impression

A page impression happens anytime when a page is getting loaded through a browser. When you navigate to a different page or even use your back button, each time you load that page counts as one page impression.

parameter

Ad type-specific attributes of an ad, e.g. the content

visitor condition

A condition from the visitor condition of the ad setting that controls who can see an ad.