Actions vary in their implementation depending on complexity. Some of them involve simple functions such as creating a mesh continuum.
In such a case the action is completed as soon as it is triggered.
Other actions may require more input; therefore they include dialogs that are modal--they must be closed before you interact with any other elements of the workspace, such as the object tree. One such action is File > Import.
In order for the action to work, you must select a file to import.
Still other actions, such as creating derived parts, use modeless dialogs.
A modeless dialog lets you interact with other parts of the workspace. This functionality is helpful when you need to check certain information before deciding what to specify in the dialog.
