What does A/B Split Testing mean?

What does A/B Split Testing mean, in e-commerce world?
“A/B Split Testing is when customers receive a message, email, or webpage view, and a different version is randomly served to different visitors or customers. Typically A/B split testing consists of two nearly-identical versions of the given source material, but with each version having one element that is different. The two “versions” are randomly served, and tracking tactics are then used to monitor the resulting actions to determine which version is most effective in generating the desired reaction.”
Introduction to A/B Split-Testing for Your Webpages, by Dr. Ralph F. Wilson
A/B Testing
A/B Split Testing