Light is essential for life. Light gives us the ability to see, and without it we would be nothing but a pile of skin and bones. Light also has three qualities that are important for understanding its effects on photography, direction, size and contrast. Understanding how these qualities affect your photos will help you take better photographs!
Direction of the light matters, as this will cause the type of light you will get in your image. The direction of your light source will either create broad or short lighting. If the light source is coming from the same side, the photographer is shooting this will create broad lighting. If the light source is coming from another area different from where the photographer is shooting, this will create short lighting. Both lighting techniques are powerful and have their own individual uses.
The size of your light source also contributes to your quality of light. A large light source will create a softer light on your subject. A small light source will create a harsh light on your subject (think of the sun). Both have unique looks and better uses.
The contrast of your light is the difference between how bright and dark the brightness values are in an image. Light can have high or low contrasts. A high-contrast subject will be relatively darker than a photograph with lower contrast, but it also may appear sharper because there is more detail visible. You can achieve higher contrast images by using a small harsh light source with no light fill.
These three qualities of light apply to any lighting scenario you may encounter, to further your education you should find images you like and re-create how they light that image.