What an advertiser defines as a sale – could be a sign up or a purchase is known as:

A conversion is the completion of an activity that an advertiser defines as valuable, such as a purchase, sign-up, or lead form submission. It represents a successful outcome for the advertising campaign. An impression is simply when an ad is displayed to a user. A click occurs when a user interacts with an ad by clicking on it. CTR (Click-Through Rate) is a metric that measures the percentage of impressions that result in a click, indicating ad relevance and effectiveness but not the ultimate desired action.