Many plants, especially flowering plants are triggered by the hours of daylight or darkness and the strength and spectrum of that light.
For most purposes, a plant in vegetative growth is usually looking for 18 hours a day of light.
Changing the light to 12 hours of daylight each day will usually trigger a plant to go into flower.
In the summer when the sun is high in the sky and the days are longer, the sun is more toward the blue end of the spectrum. This is exactly what a plant in the vegetative stage likes.
As the days get shorter, the sun gets lower on the horizon and has more of the atmosphere to shine through, which makes the light more toward the red end of the spectrum which is what some plants recognize as time to start flowering, pollinating or getting ready to produce seed.
This is how different types of lighting can greatly influence how a plant will grow during any given stage of growth.
There are only a few main types of lighting that are used in hydroponics.