What's an Heirloom?

Yellow = German Striped
Dark purple = Cherokee Purple
Pink = Brandy Wine
Red = Moskvitch

What’s the deal with heirlooms and hybrids?

Heirloom tomatoes are grown from seed that has been passed down from generation to generation for more than 50 years (general rule).  Seeds taken from these tomatoes will produce the exact same type of tomato which, as Miley Cyrus may say, is pretty cool.
In the case of hybrid tomatoes, a human plant breeder cross-pollinates two different tomato varieties to create a new variety.  The new variety has traits from both mom and dad.  If you plant the seeds from this offspring, you will get something you did not expect.  It will grow with the traits of just one of the parent plants, not both.  To get the desired new variety, human intervention is required again.  Hybrids can be nice because they often create plants with traits like resistance to disease or high yields or early production. These hybrids do require the existence of the original open-pollinated parent plants.

We love heirlooms, especially German Striped.

More if you are interested about the state of seeds:  Hybrids are NOT the GMO’s you hear about.  Most GMO controversy is about corn and soybeans and other commodities, but there are a few other vegetables that are being genetically modified in a lab.  One is alfalfa and the other is beets.  The issue for vegetable lovers is that, with the persistence of genetic modification within open-pollinated plant species, there is potential for cross-pollination that endangers those original species. Additionally, not to be a downer but, ‘organic’ status is endangered this same way (ex:  no organic alfalfa = less organic dairies).  And it seems a very slippery slope.   The Center for Food Safety is a good resource that explains the fight against GMO alfalfa and beets: 

http://www.centerforfoodsafety.org/campaign/save-our-seeds/