iPhone (/ˈaɪfoʊn/ EYE-fohn) is a line of smartphones designed and marketed by Apple Inc. They run Apple's iOS mobile operating system. The first generation iPhone was released on June 29, 2007; the most recent iPhone model is the iPhone SE, which was unveiled at a special event on March 21, 2016.
The user interface is built around the device's multi-touch screen, including a virtual keyboard. The iPhone has Wi-Fi and can connect to cellular networks. An iPhone can shoot video (though this was not a standard feature until the iPhone 3GS), take photos, play music, send and receive email, browse the web, send and receive text messages, follow GPS navigation, record notes, perform mathematical calculations, and receive visual voicemail. Other functions—video games, reference works, social networking, etc.—can be enabled by downloading application programs (‘apps’); as of October 2013, the App Store offered more than one million apps by Apple and third parties and is ranked as the world's largest mobile software distribution network of its kind (by number of currently available applications).
There are nine generations of iPhone models, each accompanied by one of the nine major releases of iOS. The original 1st-generation iPhone was a GSM phone and established design precedents, such as a button placement that has persisted throughout all releases and a screen size maintained for the next four iterations. The iPhone 3G added 3G cellular network capabilities and A-GPS location. The iPhone 3GS added a faster processor and a higher-resolution camera that could record video at 480p. The iPhone 4 featured a higher-resolution 960×640 "Retina Display", a VGA front-facing camera for video calling and other apps, and a 5-megapixel rear-facing camera with 720p video capture. The iPhone 4S upgrades to an 8-megapixelcamera with 1080p video recording, a dual-core A5 processor, and a natural language voice control system called Siri. iPhone 5features the dual-core A6 processor, increases the size of the Retina display to 4 inches, introduces LTE support and replaces the30-pin dock connector with an all-digital Lightning connector. The iPhone 5C features the same A6 chip as the iPhone 5, along with a new backside-illuminated FaceTime camera and a new casing made of polycarbonate. The iPhone 5S features the dual-core 64-bit A7 processor, an updated camera with a larger aperture and dual-LED flash, and the Touch ID fingerprint scanner, integrated into the home button, and fitness tracking facilities. The iPhone 6 and iPhone 6 Plus further increased screen size, measuring at 4.7 inches and 5.5 inches, respectively. In addition, they also feature a new A8 chip and M8 motion coprocessor. As of 2013, the iPhone 3GS had the longest production run, 1,181 days; followed by the iPhone 4, produced for 1,174 days.
The resounding sales of the iPhone, at the time, have been credited with reshaping the smartphone industry, and helping make Apple one of the world's most valuable publicly traded companies by 2011. The original iPhone was one of the first phones to use a design featuring a slate format with a touchscreen interface. Almost all modern smartphones have replicated this style of design.
In late 2014, JP Morgan estimated "iPhone percentage of the worldwide smartphone install base has been around 15% since late 2012" being far behind the dominant Android-based smartphones. In a few mature market countries such as Japan, the iPhone has a majority, an exception to Android's dominance, and Australia where Android is rapidly approaching parity. In March 2014, sales of the iPhone brand had reached 500 million devices. In the last quarter of 2014, there were 74.5 million iPhones sold, a record, compared to 51.0 million in the last quarter of 2013. Tim Cook revealed at the Apple Watch conference on March 9, 2015, that Apple had sold a total of 700 million iPhones to date. more info: https://en.wikipedia.org/wiki/IPhone