There is a lot of confusion between, open pollination, a hybrid, an heirloom and a genetically modified plant. For centuries people have been planting seeds, growing them, saving the seeds and planting it again. That is open pollination. For just as long farmers have been breeding plants naturally by creating crosses that are sustainable and will produce seeds that grow the new mixed plant. It usually means pollinating by hand between two similar plants to create an improved variety.
Heirloom plants are ancient plants that have not been hybridized and are now grown and seeds carefully kept to maintain their genetic purity. Both hybrid and heirloom are non-gmo.
Gerry Estabrook has done a brilliant job of showing you the difference. He compares GMO to hybrid and heirloom with great graphics to make it clear.
Genetic Modification is a process where scientists remove specific genes from any species—plant, animal, insect, bacterium—and transfer them into any other, something nature could never do. A bacterial gene that naturally produces an insecticide, for instance, can be inserted into corn, and the corn will produce the same insecticide. GMO, GE, GM, transgenic and genetic modification all mean the same thing.
Check out the rest of the graphics here.
Genetically modified plants require a lab and meddling in the genes by introducing an organism or part of an organism that would not survive if mixed in nature. The usual addition is a pesticide or a gene from an animal or fish. There is a lot of doubt about the long-term health of these concoctions. Check out this short video to learn more about GMOs.
Image credit: Eating Well