What Is Shadow Detail When Talking About Photography?

In photography ‘shadow detail’ refers to the detail rendered in the darkest parts of an image. Capturing shadow detail can be extremely challenging, especially when being captured in an image which includes a lot of highlights or high overall dynamic range. Shadow detail exists on the extreme fringes of contrast, and creating a balance between shadow detail and highlights is one of the most basic challenges of capturing a well exposed image; Expose too much and highlights will be overexposed, expose too little and shadow detail will be completely lost, get it just right and your pictures will come to life.

Texture rendered in the shadows of ridges of dried salt.
Dan Carr