All watches on the market today are either quartz or mechanical. And when you think of watches most people wear, they wear quartz watches.
Mechanical watches are a tad more expensive, but also more prestigious. All of the luxury and high-quality brands produce mechanical watches. A mechanical watch is a watch that uses the mechanism to measure the passage of time, as opposed to quartz watches which function electronically.
A mechanical watch is driven by a spring, called a mainspring, which must be wound periodically. Automatic mechanical watches do not need winding if they are worn for 12 hours on a daily basis. All they need is motion to keep the mainspring wound.
With that in mind, a lot of people are amazed how a watch can work without a battery, or how it can be adjusted without winding. This documentary explains that, and also gives you an idea why are mechanical watches more expensive.