A/A testing tests two identical pages against each other to ensure that there is no difference between control and variation versions and that the tool running the experiment is statistically fair.
A/B testing is a controlled experiment in which the 'control' A (original testing variable) and the B variation (a different version of the original testing variable) are tested against each other. The version that converts more recipients is considered “the winner.”
Above the fold describes the section of the web page before the user has to start scrolling, where the browser window ends. It typically gets more attention than content “below the fold.”
Average order value is a measure of the average purchase amount each time a customer places an order. The calculation is: divide total revenue from the website by the number of orders made.