There are a great many variables in photography. With that said, one of the most important elements is "light".
The "light" we capture our subjects in truly is "everything". As visual artists, we must learn what "light" is and be able to recognize good quality light for our captures. There are four types of light quality that we must learn to "see" and pre-visualize in our compositions.
The first and probably the most sought after "lighting" is what we call the "magic hour". This type of light is natural light from our Sun and can occur just before and after "sunset" and "sunrise". The Sun will be very low in the eastern or western horizon just before sunrise or sunset. This light is a beautiful golden yellow that casts long shadows upon the landscape. Also known as "side lighting" or "textured light", this light brings out texture in your subject whether it be grass on a landscape or shingles on a roof. This type of light is the most sought after light by photographers and composing your subjects in this light will really bump up your photography to another level. Subjects that do well in this light are landscapes, wildlife and architecture. This light occurs during the dawn and dusk hours and changes very quickly so you must be prepared beforehand.
Another form of light is back light. Sunlight is a natural light and if your source of light is behind your main subject, your subject will be back lit and a "silouhette" is created. The rules of photography tells us that one of our main goals is to capture a "proper exposure". Not doing so will render your main subject too dark (underexposed) or too bright (overexposed). Either one will cause definition to be lost in your subject. Back lighting your subjects will cause the front of your subject facing the camera to be totally under exposed and you will not see any definition but this is ok if your intent was to create a "silouhette" of your subject which can be a beautiful form of art. Subjects that work well would be people, statues, lighthouses, churches with steeples, architecture and any other subject that would give an visually interesting shape when back lit.
There is also "soft" light which you will learn to recognize on days that are cloudy and/or overcast. This light is spread out or "diffused" much like a diffuser that is placed over a flash to soften the light on your subject. In outdoor photography, the Sun at mid-day becomes our "flash strobe" and the clouds act as the diffuser to spread out the harsh light. This type of light is great on portrait subjects, wildlife and flowers. Subjects that display color do well in this soft light because it brings out or warms up the colors in your subject. For portraiture, soft light helps to prevent people from squinting and the softness of the light helps to smooth out the skin tones. One tip: Don't capture too much of the sky when shooting on overcast days.
The last type of light is "front lighting". This is the least attractive form of light because the light source illuminates your subject from the front and thus a more flat lighting which limits definition and structure to the subject. This form of light can still be used effectively if you know how to do it.
There are many qualities to light such as intensity, color, angle, quality, etc. and learning all about "lighting" both indoors and outdoors, bad and good, is essential if you want to create and capture stunning compositions!