Category is the group, or category, to which the action belongs. An action manager or action list displays its actions grouped by category. In addition, action bars associated with an action manager can generate user interface elements that correspond to action categories.  

Action categories group actions by similarities, usually of behavior or functionality. At design-time you can modify or set the Category for an action by selecting the action from the action list or object tree view, and choosing Category in the Object Inspector. 

ActionList 

TActionMainMenuBar 

TActionToolBar 

TActionManager