Dials is the face of the watch. A dial can have a number of configuration, various marker styles, various hands, colors, and display a number of complications.
Luminescent
Luminous markers usually fluoresce green in the dark after being exposed to light. Currently the luminous filling in the markers in none toxic, but in come vintage models, the luminescent material contains trace amounts of radioactive material.
Subdials
Subdials are smaller dials that are usually present in a watch with a number of complications. Subdials can show seconds, date, and other chronograph functions.