What exactly are Heirlooms and what makes them better?

[Brian Gallimore]

Heirloom just means antique. Most people really mean open pollinated when they say heirloom.  Open pollinated means you can save the seeds, plant them, and get a new plant similar to the plant you collected the seeds from. (as opposed to hybrid - if you plant seeds collected from a hybrid you will get something like one of the parents, but not like the plant you want)

[Brian Gallimore]

here is a better / more eloquent / more complete answer:

http://www.karenshanley.com/2008/01/whats-the-difference-between-heirloom-hybrid-and-gmo-seeds/

(hattip Kelly for the link)

[Brian Gallimore]

The difference between open-pollinated, heirloom, and hybrid seeds
By: Christy, Seed Savers Exchange | Published: MAY 2, 2012

http://blog.seedsavers.org/open-pollinated-heirloom-and-hybrid-seeds/