Apple has sold millions of iPhones since their release in 2007. The iPhone was voted Invention of the Year by Time magazine and it quickly became one of the most in-demand consumer items on the market. They have sold over 21 million units as of April 2009 and they will no doubt sell many more over the coming months.

If you are wondering why the iPhone is so popular then you need to take a closer look at the features on offer. It is a slim, sleek and attractive looking device but the sales are about much more than the visual style.

Apple has built a reputation for solid design and they are good at creating desirable technology. The iPhone measures 4.5 x 2.4 x 0.48 inches and it weighs in at 4.7 ounces. There have been many attempts to clone the iPhone and cheap knock offs proliferate but none of them have managed to achieve the same slim design.

The clever appeal to tactile satisfaction is extended to the touch screen. Of all the iPhone features the touch screen technology has to be the single biggest selling point. You can navigate through menus and browse the web with a flick of your finger. The interface is perfectly weighted and very satisfying to use. While this technology has been emulated in other devices no-one has gotten the same satisfaction into the operation of their touch screen.

The screen is a 3.5 inch widescreen display and it can be operated with a stylus as well as your fingers. It features a high resolution of 480 x 320 pixels which is way beyond virtually all other mobile phones.

The iPhone also contains three sensors, an accelerometer, a proximity sensor and an ambient light sensor. The combination allows for extremely efficient operation and the sensors can also be utilised by applications to create interesting options.

The attractive iPhone features keep coming and the device also supports audio and video files in various qualities. At the high end it is capable of playing music and video which is far superior in terms of quality than the vast majority of content which can be handled on other cell phones.

The latest iPhone features 3G compatibility which allows fast downloads and streaming content from the Internet. It is has Wi-Fi and Bluetooth capability and can be used on virtually any network.

The iPhone can be connected up to a PC or Mac via USB and using the iTunes software downloading new content onto the device is quick and painless. There are thousands of applications available and the choice is way beyond the vast majority of competitors.

The device can recharge while it is connected to a computer and a fully charged battery will provide 5 hours of 3G talk time or 10 hours of 2G talk time. Alternatively a full charge will provide up to 300 hours of standby. These statistics are very respectable when compared to other cell phones.

The iPhone has more features than the vast majority of other cell phones. In fact one of the few features it lacks is the ability to record video footage and according to rumours this feature will be added into the next generation. The iPhone ships with a stereo headset and mic, a dock connector to USB cable, a USB power adaptor, a cleaning cloth and a sim eject tool.

It has also been designed with the environment in mind and the design does not use PVC, bromine or mercury. It is a tough device which can operate comfortably within the 0 to 35 degree centigrade temperature range.

All in all the iPhone is packed with terrific features and the only area where it struggles with competitors is price. However quality is always expensive and the iPhone still represents good value for money.