Multivariate testing in marketing is when you test different versions of a marketing message to see which version works best. It's like running an experiment - you create different versions of a website or ad, then you show them to different people and see which one gets the best response. The goal is to use the version that is most effective in getting people to take action (like buying a product, signing up for a newsletter, or clicking on a link). It's different from traditional testing, which uses one version of an ad or website. Multivariate testing helps you to find out which elements, such as colors, images, words, and even placement, work best.