This video shows you how to build multi-entity segments in Adobe Experience Platform’s Segment Builder. Multi-entity segmentation, or segmentation across classes, allows you to build segments combining data based on multiple XDM classes. For example, you could have a dataset built on the XDM ExperienceEvent class capturing product ids when customers make a purchase and another dataset built on a custom product class, containing the catalog details of each product id (e.g. color, size, category, etc). If you establish a relationship between the schemas, you can then build segments based on fields existing in both schemas (e.g. people who bought jackets).
For more information, please see the Multi-entity segmentation (documentation).