It is also known as split testing.
It is a form of experiment between two versions of a landing page or web page to see which page performs or get conversions better.
As the name suggests, two versions (A and B) are compared, which are identical except for one variation or more that might affect a user’s behavior. Version A can be the currently used version, while version B is modified of the version A. From an e-commerce website point of view, the purchase funnel is typically a good example for A/B testing, as even marginal improvements in drop-off rates can represent a significant gain in sales. Significant improvements can sometimes be seen through testing elements like layouts, copy text, images, and colors, but not always.