The Search function is your best friend! Just look up light cycles ect... or get a cannabis grow book that explains everything like this one here..
https://www.discountbooksale.com/p72589/Marijuana-Horticulture-The-Indoor-Outdoor-Medical-Growers-Bible.html
That book is by far the best there is.
The plants life focuses around the Sun, which depending on the time of the year, has longer and shorter hours of light. You are basically mimicking natures sun. In the spring, the light is longer and the plant focuses on growing larger. This period is called the vegetative state and requires a longer period of light. Hours are usually 18 hours of light-24 depending on which method you adopt indoors .The color, or Kelvin(K), of the bulb is also a different color to help the plant in its veg stage (6500k). When summer comes and goes the light in the day gets shorter and the plant knows its life cycle is coming to an end. This is known as the flowering stage. The plant is trying to make bud and produce trich's to catch the pollen and seed. It is reflected in the grow room as 12 hours of light and 12 of darkness. The color of the bulb is more amber (2700K) and reflects the autumn sun.
Since you are restricting the plant from catching pollen by not having a male present, the plant will keep producing bud. At harvest, the plant is cut down and you start all over again.