All questions related to Sitecore Experience Optimization feature. It may include A/B testing, multivariate testing.

Content tests let you test alternative variants of your website's content to find out which pages, components, or combinations of components are the most effective with visitors. The content or components that you are comparing in a test should be designed to achieve the same goal.

You can quickly evaluate the test results and gain insight into the content that functions best with your audience. This can help you create more successful campaigns with higher goal-conversion rates.

https://doc.sitecore.net/sitecore_experience_platform/analyzing_and_reporting/experience_optimization__content_testing

https://doc.sitecore.net/sitecore_experience_platform/analyzing_and_reporting/experience_optimization__content_testing/content_testing_overview

https://doc.sitecore.net/sitecore_experience_platform/analyzing_and_reporting/experience_optimization__content_testing/experience_optimization_and_content_testing_glossary