Mechanical watches have three major operating systems. The first is where the power is stored. This is a spring called a “mainspring” which sits inside of a container called a “barrel,” and it will need to be wound either manually by turning the crown with your fingers or via a weight called a “rotor” that spins around in a “self-winding” or “automatic” watch with the motion of your wrist to power it. Attached to the mainspring is a system that regulates how slowly the spring unwinds, which is called the “regulator.” This is mainly two components—an oscillating wheel known as a “balance wheel” and an “escapement,” which moves that power from the unwinding spring to the mechanism that tells the time. Watch lovers like to refer to the regulator as the “heart beat” of a watch, because the beating “balance spring” attached to the balance wheel not only resembles a heart but is the main source of a mechanical watch’s life.
The idea of the regulator is to ensure that a reliably consistent amount of power is flowing from the slowly unwinding mainspring to the “gear train” which in turn moves the hands which tell the time. The length of time a mainspring will unwind when fully wound is known as a watch’s “power reserve,” which is usually around 40 hours. If this all sounds too abstract then YouTube has a lot of videos showing how this works in glorious animated detail.
Moving away from the movement, the watch face is often called the dial. Over the dial is a crystal to protect it, which in all good watches is made from synthetic sapphire crystal (because it is very clear and very hard – tough to scratch). The main body of a watch is called the case, and people use the case width to describe its size. Watch size is a big deal and watch lovers like to argue about what sizes are best. Historically, men’s watches were smaller and today people often prefer wearing larger watches. To put these sizes into perspective, most men today prefer wearing watches sized from about 40 to 44mm wide.
Besides stainless steels, wrist watches use a lot of materials you probably expect like gold, titanium, and other metals and precious materials. Exotic and high-tech materials are now popular in modern watches such as zirconium oxide ceramic, carbon fiber, and silicon (used as a replacement for some metal movement parts in some watches).