Phone

• The main feature of the iPhone is the ability to make and receive phone calls from wherever you are. You can use your iPhone with either AT&T's network or Verizon's network, but you have to decide which carrier you will use when you buy the device. The iPhone includes a number of standard phone features, like caller ID and voicemail. The device even has a front-facing camera so you can make video calls to other people who also have an iPhone 4.
  
  

Camera

• In addition to the front-facing camera, the iPhone also has a rear-facing 5 megapixel camera. The camera has an LED flash, a 5X digital zoom, single tap focusing and a host of imaging controls. The camera also functions as a high-definition video recorder, and there is software on the iPhone that lets you edit your movies right on the device.
  
  

Display

• The new retina display on the iPhone 4 feature 326 pixels per inch, which is four times the amount of pixels on the earlier version of the iPhone. The pixel density is so high that the human eye cannot make out individual pixels, resulting in images that are extremely sharp and clear.
  
  

Email

• The iPhone will let you access and send email from a number of different accounts, all using the same email program. The iPhone is designed to work with a number of popular providers, like Yahoo! Mail and Gmail, but can you can also set it up with any email service if you know the correct information. The device lets you access each email account individually, or you can have all the messages sent to one combined inbox.
  
  

Multitasking

• The iPhone 4 has a new way to run applications in the background without draining the battery and hogging the processor power. This feature lets you open multiple applications and switch between them instantly. When you leave an application, you will pick up right where you left off when you device to go back to that app.
  
  

Gyroscope

• The iPhone 4, like many smartphones, contains an accelerometer so it can determine how fast you move the device, but the iPhone also contains a gyroscope. The iPhone gyroscope operates on six axises, allowing application developers to design more intricate apps revolving around moving the iPhone.
  
  

Applications

• The iPhone gives you access to Apple's App Store, where developers will post and sell applications designed to run on the device. Currently there are hundreds of thousands of applications available for downloading, ranging from free, simple games to expensive productivity solutions. Many of the applications also integrate with other iPhone features, like the installed GPS, to enhance your overall smartphone experience.