Automatic Watches: A rotor on the movement keeps the watch powered by the motion on your wrist. If worn everyday, an automatic watch will run for life (or until it breaks). Automatic watches generally have 100's of parts inside their small cases. If an automatic watch has stopped, it is best to wind it via the crown 20-30 times to give it a good kick start. If not wound manually, wrist motion is generally not enough to keep it running accurately.
Quartz Watches: The quartz movement became common for watches in the 70's. They are powered by a battery and need little maintenance except for a battery swap every year or so. They are highly accurate compared to mechanical watches.
Manual Wind Watches: A manual wind watch must be wound every one or two days by the crown in order to run. Even with that perceived inconvenience, they are still produced in Switzerland and can even be found on watches well over $5000. Many collectors find them highly desirable. It is easier to make a thinner and lighter watch without the self-winding mechanism. Some unique movements can reserve up to 8 days of power and will usually have a power-reserve indicator on the dial.