iPhone is a cellular phone developed by Apple and available on the AT&T and Verizon networks. The iPhone is best known for its full-face LCD touchscreen and colorful graphical user interface.
In addition to functioning as a cell phone, the iPhone is also a fully capable iPod, able to store and play back music and video.
Web browsing on the iPhone is via Apple's Safari web browser.
The most popular feature of the iPhone is "Apps," small applications that can be downloaded to the phone. These can range from games to Facebook and Twitter.
Nearly all products designed to work with an iPod also work with the iPhone, like iPod docks. The added abilities of WiFi and Internet connectivity allow for additional functionality in interacting with gear. For example, the Remote app lets your iPhone control playback of your iTunes library. You can also control your Apple TV using the iPhone as a remote.
The iPhone is managed using iTunes, just like an iPod.
The iPod touch from Apple is effectively an iPhone without the phone portion.