Multivariate feature flags allow you to use custom variations to dynamically configure flag behavior. Traditionally, feature flags return a boolean value: true or false. This works well for basic end user management and a kill switch.
In addition to boolean values, multivariate flags allow you to return strings, numbers, JSON arrays, and JSON objects. This makes it possible to do configuration management via feature flags and manage plans/complex functionality.
It also makes it possible to manage multiple variations of a feature. For instance, you could manage multiple checkout flows (one-click, two-click, original) and gradually roll out each of those variations to a different subset of your users.