The iPhone™ is a line of smart phones first introduced by Apple in 2007. It functions as a camera phone, including text messaging and visual voicemail, a portable media player, and an Internet client, with email, Web browsing and Wi-Fi connectivity.
The iPhone's interface is one of the most sophisticated ever introduced on a consumer product. Almost all input is given through the touch screen, which understands complex gestures using multi-touch. The iPhone's™ interaction techniques enable the user to move the content up or down by a touch-drag motion of the finger. For example, zooming in and out of webpages and photos is done by placing two fingers on the screen and spreading them farther apart or bringing them closer together, a gesture known as pinching. Scrolling through a long list or menu is achieved by sliding a finger over the display from bottom to top, or vice versa to go back. In either case, the list moves as if it is pasted on the outer surface of a wheel, slowly decelerating as if affected by friction. In this way, the interface simulates the physics of a real object.
Other user-centred interactive effects include horizontally sliding sub-selection, the vertically sliding keyboard and bookmarks menu, and widgets that turn around to allow settings to be configured on the other side. Menu bars are found at the top and bottom of the screen when necessary. Their options vary by program, but always follow a consistent style motif. In menu hierarchies, a 'back' button in the top-left corner of the screen displays the name of the parent folder.