Try these links for a sensible explanation. They say the same thing but in different ways; you might prefer the Houston link because it has more info.

http://www.houstongardening.info/tiplinks.htm

http://www.ext.vt.edu/departments/envirohort/factsheets3/general/FEB90PR2.HTML

or to be really, really specific in definition (and I suspect the tomato poster was using parens to indicate nom. illeg.):

http://www.northernontarioflora.ca/definitions.cfm

BTW, although considered an 'heirloom' tomato (I think the seed was originally available in the late 1800's), Brandywine has several distinctly different forms, depending on who is describing it and which seed produced the tomato. You will find it described as yellow or pink or reddish or deep red, and in sizes all the way from 'plum' to 4 or 5 oz.

Here is a link that might be useful: horticultural terminology

Often, you'll see the words "cultivar" and "variety" used interchangeably, but technically, there is a difference. A variety can be grown from seed, but a cultivar is propagated vegetatively, usually by rooting stem cuttings or dividing and replanting pieces of root taken from the parent plant. Strains are varietal mutations that has been chosen and propagated for an improved or unusual characteristic.

Al

Thank you both, I think its clear in my head now :). It really is quite technical, it took me reading all 3 explanations to finally get it straight. Now I'll even understand the plant labels better.

Thanks so much
Kristi