Timeshares are part of a nearly half-century-old business model. They have grown from an inauspicious beginning in Europe into a worldwide force controlling millions of vacations and billions of dollars. Still, the industry is eager to reach out to people from all walks of life and all income levels, hoping to tap the vast pool of remaining vacationers who can afford a timeshare but haven't yet purchased one. Will you buy into the global trend? First, you need to learn what the craze is all about.