The Relationships View provides the equivalent of a database diagram specific to the tables loaded to the model for the dataset. The relationship lines distinguish the one, or parent, table of each relationship from the many, or child, table. A solid line indicates that the relationship is active, while a dotted line denotes an inactive relationship that can only be activated via the USERELATIONSHIP() DAX expression. Additionally, the arrow icons on the relationship lines advise whether cross-filtering is single-directional (one arrow → one way) or bidirectional (two arrows).

In the following screenshot from the Relationships View, only the Reseller to Reseller Sales relationship is bidirectional and the relationships between all tables displayed are active:

Given the bidirectional cross-filtering relationship, a filter applied to the Employee table would filter the Reseller Sales table and then also filter the Reseller dimension table. Double-clicking a relationship line prompts the Edit Relationship dialog to optionally modify the columns defining the relationship, the cross-filtering behavior (single or bidirectional), and whether the relationship is active or passive. 

A gray font indicates that the given column is not visible in the Report View. For certain tables that are only used for internal logic, such as bridge tables or measure support, the entire table will be grayed out and invisible to the Report View. Synonyms can only be accessed via the Relationships View and can serve to improve the accuracy of Power BI's Q & A natural language queries by associating terms with tables, columns, and measures of the Data Model.