A/B testing, also known as split testing, is a method used in digital marketing to compare two different versions of a web page or marketing asset. It works by dividing the audience into two groups and exposing each group to one version (A or B) of the asset. The performance of each version is then measured based on specific metrics, such as click-through rates or conversions. By analyzing the results, marketers can determine which version performs better and make data-driven decisions to optimize their marketing strategies.