I know cell phones do everything for us now a days.  But the cell phone will never look as good on your wrist as a beautiful watch. Watches have been around since the 1500's so there has been plenty of time to perfect what was already a super innovative idea. Watches fall into two basic categories, mechanical and quartz. Mechanical watches obviously are the originals as batteries weren't invented until much later. That being said, quartz movement (battery operated) watches represent the majority of watches sold in America. Mechanical watches tend to be made in fewer numbers as the movement is a little more complex and costly to make. Mechanical watches are powered by winding a mainspring within the movement. How the watch is wound may differ.  For instance, automatic watches such as those made by Rolex, use motion and gravity to automatically wind the mainspring.  Patek Phillipe uses the traditional stem and crown to wind the watch.  Both of these are examples of mechanical watches. Often times these companies will have a crystal on the back as to show the working of the watch. Doing that serves no real benefit other than it looks really neat.
Citizen watches are slightly different. They operate on a cell which is powered by light. This is called an Eco Drive. From thin and tiny to big and chunky watches come in all varieties and price ranges. This is definitely a great fashion statement for both men and women.