USB On-The-Go, often abbreviated to USB OTG or just OTG, is a specification first used in late 2001, that allows USB devices such as digital audio players or mobile phones to act as a host, allowing other USB devices like a USB flash drive, digital camera, mouse, or keyboard
to be attached to them. Use of USB OTG allows these devices to switch
back and forth between the roles of host and client devices. For
instance, a mobile phone may read from removable media as the host
device, or present itself as a USB Mass Storage Device when connected to a host computer.
