Contrast is one of the most important elements in photography. I'm not talking -only- about the slider in your photo editor to manipulate the tones of the image.
Contrast means difference. Creating difference between your subject and everything else, you are able to tell a story.
This can be achieved using the differences in color and luminance, but also using shapes, textures and more.
While we seek contrast between the subject and the rest of the photo, we want to minimize it within those elements - thus increasing it between them. One of my favorite techniques to achieve this is long exposure photography: smoothing out water, for example, we remove contrast from it hence increasing that contrast between the water and our subject.
I show you some examples of this and other techniques in this video: