From Nielson Norman Group: https://www.nngroup.com/articles/dot-voting/
Summary: By placing colored dots, participants in UX workshops, activities, or collaborative sessions individually vote on the importance of design ideas, features, usability findings, and anything else that requires prioritization.
There are few UX-workshop activities that work well in any situation. Dot voting is one of them.
Dot voting is a simple tool used to democratically prioritize items or make decisions in a group setting. It is an easy, straightforward way to narrow down alternatives and converge to a set of concepts or ideas.
Definition: In dot voting , each individual in a group is given a number of tokens (“dots”) that can be each assigned to an alternative which is part of a set of alternatives.