What makes a smartphone "smart"?

Generally, the term "smartphone" refers to any device that operates on one of the following operating systems: RIM BlackBerry OS, iPhone OS, Windows Phone from Microsoft, Android, Palm webOS, Linux or Nokia's Maemo. Along with complete phone functionality, these devices support full HTML email, web browsing, calendar management and the ability to sync with personal computers. Most smartphones also have access to one or more "app stores," which allow customers to browse and purchase thousands of different mobile applications from an increasing number of developers. If you're looking for an experience similar to that of a laptop computer, a smartphone might be right for you.