Sure, a smart phone can make a phone call, but that's just a fraction of what it can do.
You can keep your calendar, store and play your music, watch TV shows - even feature-length movies.
And, of course, smart phones let you update your Facebook status anywhere … keep on top of your Twitter feed … take photos and shoot video.
Since it went on sale, there's been plenty of buzz about Apple's new iPhone 4-S, and Consumer Reports testers say it turns out to be a great phone.
The 4-S is faster than the iPhone 4, and the upgraded camera takes better pictures.
The voice-activated personal assistant, Siri, also works well - and it even has a sense of humor.
Mike Gikas with Consumer Reports asks, "What is the meaning of life?"
Siri responds, ""Beep." "I can't answer that now, but give me some time to write a very long play in which nothing happens."
But Consumer Reports says there are plenty of other smart phones out there that perform just as well, or even better, than the 4-S.
Mike says, ""For example, several phones we tested weigh less than the 4-S and have larger screens."
Like the Samsung Galaxy S-2, on the right. A bigger screen is great for Web browsing and video.
Another important consideration - speed.
Mike explains, "Many of the Android phones we tested run on 4G networks, and are faster than iPhones. That means content downloads more quickly and videos run smoother."
If you have Verizon, Consumer Reports top rates the Motorola Droid Bionic.
If you use Sprint, T-Mobile, or AT&T, the Samsung Galaxy S-2 topped the ratings.
Consumer Reports says there is one aspect of the iPhone that's a real selling point - compatibility.
If you own other Apple devices, like an iPad or a Mac computer, getting pictures, video, and music from one device to another is a breeze.