The Map Manager can display the same layer with four different symbology themes or styles:

Default Display - Displays the features using the symbology and scale based display rules as defined in the active Bentley Map project. There are no editable options when this mode is selected.

User Defined 1, 2 and 3 - Overrides the feature definition symbology and display scales with new symbology. The new symbology is based on a combination of attribute queries and display scales that are defined in the Class Properties and Symbology Settings panes of the dialog.

The selected Thematic Definition Set determines which symbology theme is applied to the selected layer.