While terming this to be "gender" is not accurate, as bell pepper plants are hermaphroditic, this does appear to be a method used to identify which type of bell pepper is best for each purpose - either cooking, eating raw or for seed collection.

There is a simple method for identifying which bell pepper has the traits you desire. Look on the underside of the pepper, the ones with four bumps are "female" and those with three bumps are "male". The ones termed "female" peppers, or those with more bumps, contain more seeds and will be used largely for collection of seeds and replanting (hence "female"), but are also sweeter and better for eating raw. The ones with three or fewer bumps are better for cooking and contain fewer seeds.

source: Homesteading Self Sufficiency Survival