Auto seeds go "automatically" to flower when they are ready. They do not need the light to change to 12/12 to flower. These can produce male or female plants. They are created by breeding a Sativa or Indica with a C. Ruderalis. This species of Cannabis comes from the far north, in Russia, and cannot count on the sun to tell it when to flower so it does it by time instead.
Feminised seeds are seeds that have been pollinated by another female plant that was forced to become a hermaphradite by treating the plant with gibberellic acid, a plant hormone. These seeds have a higher probablity of becoming female but they also have a higher probability of becoming a hermaphradite.
So, autoseeds are easy for beginners since you don't have to know when to put them into flower and feminised seeds let you get more females.
