Feminized seeds are female, created by spraying chemicals on a female plant which causes her to produce male sex organs.
The pollen produced by the aforementioned male sex organs, is female, therefore producing only female plants.
Regular seeds are both male and female.
Auto plants are regular plants which have been bred to a ruderalis.
A ruderalis is a species of cannabis that doesn’t rely on photoperiodism to produce flower due to the fact that it evolved in a cold climate that had a short growing season, and it has low flower production.
Breeding revolves around the goal of retaining both, the bud production of the modern marijuana varieties, and the non-photoperiodism of the ruderalis.
Autos and photos are both regular plants until someone reverses a female, of either variety, and creates feminized seeds.