Me Again about my Sunset apple.

Another thing that I found one website mentioning is that the Sunset
Apple was a 'heritage' variety.

I have come across a number of places where they mention 'heritage'
varieties of this that and the other but I am becoming rather
suspicious that this isn't as rigorous a label as one might expect.

Can anybody tell me exactly what constitutes a 'Heritage' variety? Is
there a set guideline, or is it more of a marketing gimmick intended
to catch the romantic gullible gardener?

Thanks
Steve