According to Diamond, not all places invented food production (agriculture) on their own. They did not all domesticate their own plants. Instead, many places simply got plants that were already domesticated from other people. These plants are what he calls founder crops.
The importance of founder crops is that they allowed these areas to have agriculture. Agriculture is the factor that allowed them, eventually, to develop guns, germs, and steel. This was especially possible in Eurasia because its long east-west axis allowed for the same founder crops to be used various times in various places.
Founder crops were varieties of plants that were easier to grow and required less effort to yield the same quantity of food. They were either adopted by the native people of some regions themselves, who then partly or completely abandoned their hunter- gatherer way of living. In other instances the founder crops were brought by people from other regions.
These invading communities used the founder crops as a means to displace the local communities. The crops made their way of living easier compared to the local communities as they had to spend less time in gathering food. They had a more secure source of food as well as more time to utilize for other purposes.