Both film and digital cameras can only capture what is but in front of them and then but imperfectly. Dynamic range limits what they can capture.
This is where the art of burning and dodging comes to the craft of photography.
My goal when I shoot an image is to get the most I can on film/digital capture so that I have the most information I can get in the image. Once I have the image then I can orchestrate the image to make it the best I can.
Generally, when we see an image, our brain will make the corrections as to exposure and contrast. Yet film and digital can quite get it all, let alone keep them in context.
Basically, I use a little bit of dodging to lighten things need to be brighter that I think need to stand out of my image a bit more. Skies usually need to be darkened by burning to bring them down to balance out the contract/brightness of the image. Burning also can be used to hide parts of an image that without, would simply stand out and become a distraction, such as trash or other objects that can't be moved or if cloned from the photo, would change the authenticity of the image such as for news or documentary work.
One of the best bodies of work that I can think of that used not only burning and dodging to its fullest, but bleaching and intensifying his work was W. Eugene Smith, especially his latter work at Minamata. Ansel Adams was also a master of burning/dodging. For him it was to create a print that matched his previsualization of the the image in the field to how it would eventually be crafted on the paper. His work is still printed today for the Ansel Adams Gallery in Yosemite by Alan Ross now for nearly 40 years after Ansel's death using the original dodging-and-burning notes for each of the prints to convey what Ansel's vision of the photograph should convey.
Looking at Ansel's Moonrise photos though the years, one can see how it went from a literal black and white rendering of the fleeting moment he recorded back about 1941 to his later prints showing an intense, jet sky, glowing moon and clouds and the church and cemetery on the horizon on the bottom of the print. Burning and dodging took the print from but a simple snap-shot to a memorable work that still evokes emotion 80 years since Ansel snapped the shutter.
Today we have the technology to do what Ansel did in a darkroom and by trial, error and starting over on each print, to being able to do a master image complete with not only our burning, dodging for exposure/contrast and easily do the same with color, sharpness and so many other variables. Yet sometimes that makes an image almost too clinical in its craft; lacking in the personalization that came organically when each print was burned and dodged by hand in the darkroom.
I tried to add a couple of examples of burning and dodging compared to the original but having issues with it right now...