Heirloom seeds are open pollinated and produce the same plant year after year. All you have to do is save the seeds and replant the following year. These seeds usually have a historical past to them and have been carried down from generation to generation.
Most seeds that are sold at retail stores are hybrid seeds. They are seeds that have had their genetics changed. They are the results of many different plants combined to create a new variety of plant. They usually produce more crops, produce a more uniform product than an heirloom plant, and are usually disease and drought resistant. There is nothing better tasting than a true heirloom vegetable. They are a little harder to grow and need more care to raise than a hybrid, but it is well worth every minute of the time.