The commands
, , and only appear in the menu if a text layer is present.When you add text to an image, GIMP adds specific information. This command lets you discard this information, transforming the current text layer into a normal bitmap layer. The reason to do that is not evident.
Note that this transformation of text into bitmap is automatically performed when you apply a graphic operation to the text layer. You can get text information back by undoing the operation which modified the text.