In Multivariate Testing you select different elements on your website or landing page (such as headlines, images, buttons, etc). Different versions of selected elements are created and combined. Then you split your traffic amongst those combinations to analyze which one gets maximum conversion rate or sales. The winning combination of the website is later chosen to be implemented permanently. See following image for illustration
In Visual Website Optimizer, we use full factorial methodology for multivariate testing.
Please see following links for tutorials: