A dietary mineral is a chemical element that a living thing needs to be part of what they eat, other from the four elements carbon, hydrogen, nitrogen, and oxygen which are already very common in living things.
One example of a dietary mineral is calcium, which humans and many other animals need to build strong bones and teeth, among other things. Iron is another mineral, which you can find in red meat. It is important for us to have iron as it creates red blood cells. Other common minerals include potassium and phosphorus.