Butterflies obtain nectar, a food source, from flowers. When they fly from one flower to another, they disperse pollen. Which type of interaction do the butterflies and flowers have?

This is an example of mutualism. In mutualism, two organisms have a relationship which benefits both organisms. In this example, the butterflies benefit from food, and the flowers benefit by having their pollen spread.

Since both organisms are benefiting from the relationship, it is called mutualism.