TL;DR
Conversions represent the marketing metric meant to measure the point at which a website visitor or potential customer takes the desired action, this way transforming itself from a simple viewer into a buyer, subscriber, follower, etc. In the vast majority of cases, the number of conversions dictates the success of a business.
About Conversions
The conversion is a marketing metric that defines the number of visitors or users who got convinced to take a certain action that resulted in the benefit of a business. For example, if two people enter on an e-commerce website and one decides to leave while the other decides to buy a product, the second one counts as a conversion.
Conversions are different for each business, as one might consider a purchase a conversion, while others can count a subscription or a registration as a conversion. It all depends on the type of business and the preset goals.
In the app, users decide on their own which web pages count as conversions and are able to configure the ones that they consider important for their business, to be counted as conversions in the Overview Dashboard and in the Pages Menu → Conversions.