Autoflowering MJ are plants that go into flowering on there own. They do not require a 12/12 light sched for flowering. They also grow pretty fast. My last harvest was 2 autos 65 days seed to harvest.
Autoflowers are great plants if you hate all the talk about light schedules and all that. Giving an autoflowering strain 20/4 light will maximize final yield. Generally speaking, autoflowers yield less than photo-period plants simply because autoflowers give you no control on when you wish to flower; they do that on their own. You can get a good amount off autoflowers though.