iPhone is a line of smartphones designed and marketed by Apple Inc. It runs Apple's iOS mobile operating system. 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 texts, GPS navigation, record notes, do mathematical calculations, and receive visual voicemail. Other functions—video games, reference works, social networking, etc.—can be enabled by downloading apps.