If we select a simple mask such as AlbumArtistorArtist/Album/Track - Title in the dropdown and then Edit we see
The AlbumArtistorArtist/Album/Track - Title part is just the name of the mask, it could be anything but clearly makes sense to try and describe what the mask does with a sensible name.
The actual mask is defined in the Mask field, it is written in Javascript expression language
The Example field changes to reflect how the mask would affect the filename of an example file
The Mask Fields lists all the metadata fields that can be used in the mask
The Javascript User Defined Functions list all the predefined functions we have written that can be used in any of rename mask, this is additonal to all the satndard functions that come with Javascript Expression Language.
We explain this mask in more detail in the next tutorial.