An attribute set defines the display and format properties of a field component that are displayed in a data-aware control at design time. It also defines any constraint and default properties of the field component. Attribute sets are only available on Windows. 

Attribute sets are stored in the data dictionary by name so that at design time developers can create and apply the same set of attributes to different field components in one or more datasets. When an attribute set is assigned to a field component at design time and that field component is owned by a TQuery or TStoredProc dataset, AttributeSet contains the name of the assigned attribute set. 

TDataSet 

TQuery 

TStoredProc