For Conceptual Mass models, this icon provides various settings for Mass and Detailed models. For instance, if View Rotation is checked here this will rotate the Revit model when a Façade or Surface is selected in the Façade Navigator. User preferences may be set here. Settings are covered in more detail later in Section 9.0.
There are tabs for Common (send an error log to us, change units for results or enable automatic View Rotation when highlighting Surfaces etc) and Conceptual Mass settings (default values for cill and head heights for notional glazing zones etc).