Segments are configurable groupings of People, Accounts, Opportunities, and Activities that leverage selectors to define the criteria for the groups. 

Segments are built and managed in Engagio and can be configured without the assistance of a Salesforce Admin.

Segments are mutually exclusive, which means that the order of the Groups matters. If a person, account, opportunity, or activity qualifies for multiple Groups within a Segment they will belong to the first Group that they qualified for.

Segments will always contain a Default Group, the default is for people, accounts, opportunities, or activities that fail to qualify for any of the Groups within the Segment.