USB On-The-Go often abbreviated USB OTG or just OTG is a specification 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 mouse or keyboard to be attached to them. Unlike conventional USB systems USB OTG systems can drop the hosting role and act as normal USB devices when attached to another host. Please ensure the peripheral you are connecting also supports OTG or it may not be compatible. Devices such as printers etc require drivers to function and the phone you are supporting may not support these.
USB OTG devices are backward-compatible with USB 2.0 (USB 3.0 for SuperSpeed OTG devices) and will behave as standard USB hosts or devices when connected to standard (non-OTG) USB devices. The main exception is that OTG hosts are only required to provide enough power for OTG devices.
To be compatible your phone or tablet must support OTG and have a USB 3.0 10pin socket. For example: