The iPhone is a mobile phone, digital music player and internet access device combined in a single slim package.
Other "smartphones" have similar functionality but Apple's reputation for ease of use, based on its Macintosh line of computers and iPod music players, has made it the most desirable gadget of 2007.
The iPhone has a touch screen and clever software which makes it easy to navigate with your finger. Built-in sensors mean that when you turn the iPhone on its side the screen is automatically rotated.
It can access the internet over the mobile phone network but also through Wi-Fi networks or hotspots which are becoming more common in public spaces such as hotels and airports.
Apple said it would "reinvent the phone" when it introduced the iPhone. "iPhone is a revolutionary and magical product that is literally five years ahead of any other mobile phone," Apple chief executive Steve Jobs said with characteristic modesty.
Long queues formed outside many Apple shops in the US when the iPhone went on sale there on June 29th. Despite this, few stores sold out.
By the middle of last month more than 1.3 million iPhones had been sold in the US.
No date has yet been given for a launch in Ireland but it is expected to be available in the first half of next year.
Industry insiders expect it to retail for about €400 in Ireland.
Based on what Apple has done in the rest of Europe, customers will also have to sign a new two-year contract with whichever mobile network Apple partners with.
This is likely to involve an additional monthly spend of at least €50.
The iPod Touch provides most of the same functionality as the iPhone, except with no mobile phone, and is available in Ireland now for about €300.