Here you can find information about the file and its various audio properties. Clicking the "Additional Information" button will pop up an extra window provided by the input plug-in responsible for handling the track.

If a track contains an ID3 tag, its contents can be examined (but not edited) here (assuming "Ignore ID3 tags" is not turned on from Options dialog->General). ID3 tag consists of information frames. All frames contained in the tag are listed in the list box. You can view the contents of a frame by selecting it from the list. If the selected frame contains an attachment, the "Save attachment to file" button will become enabled.