I'm told that if you save and plant the seed from a hybrid tomatoe plant, that the resulting plant will not be the same as the 'parent' plant. I understnd that. What I don't understand is how they get the hybrid seed to start with. Is it a matter of a certain type of cross pollination that produces the hybrid seed variety that is being sold?

The seed from the hybrid plant won't sprout. Unless it is a heritage type seed.