The Online Family answers:

The new breed of "smart phones" (Sidekick, Treo, BlackBerry and iPhone) come with features and functionality that go way beyond simply making a phone call.  You can send email, manage your appointments, contact people in your address book and surf the web. Smart phones are great for people who essentially need a portable computer, but don't want to carry a laptop.

That said, these days, some regular cell phones actually come with some of the same features of a smart phone -- at a fraction of the cost. The main difference is ease of use. Smart phones come with mini keyboards and bigger screens that make it easier to type messages or surf the web. Traditional cell phones, on the other hand, require you to use your phone keypad to send text messages or search the Internet, which can be more cumbersome and time-consuming.