Multivariate testing (MVT) is similar to A/B testing, but the amount of variables used in each test differs. A/B testing only uses one variable, while MVT uses multiple variable combinations to see which one is the most effective.
For example, if a marketer wanted to test multiple versions of the same website, they could change banners, colors, text, buttons, etc. to see which combination of those variables wielded the most favorable result.