Frames and dialogs differ in the following ways:
Dialogs don't appear in the operating system's task bar. Frames do appear in the task bar.
Dialogs are usually created by a frame which becomes the owner/parent of the dialog --- if the frame is closed then any dialogs that the frame created will be closed too.
Dialogs can be made modal which means that the user can not access any other windows until they close the dialog.
Generally you have one frame that is the main window for the system and all other windows that are created are modal dialogs. This helps make the system significantly easier to create since we don't have to worry about bugs that can occur when the user has access to many dialogs at once.
In our system, the
MainMenu frame that you created as a project task last week is the primary window, and all other windows will be modal dialogs.