Dial
In the context of mechanical watches, the dial is the flat surface with markings on it.
The hands in front of the dial point to these markings to indicate the time (and other things too, if the watch has complications), while the inner workings of the movement are hidden away behind it. The dial and hands combined are the face.
An open heart watch has a window (often simply a gap) in the dial, revealing the beating balance wheel inside. A skeleton watch goes even further, stripping the dial — and even the plates and bridges of the movement itself — back to its bare essentials, to reveal as much of the watch's process as possible.
Mechanical watch parts: Blued screw | Dial | Swan neck regulator
