OTG USB (On-The-Go) is what the USB ports on the new generation of smartphones and tablets are called. These allow you to connect a flash-disk, external hard-disk, keyboard, mouse, card scanner, hub, etc. using a micro USB connector (or possible using an USB adapter).
OTG flash drives work with mobile telephones and tablets, which support OTG function, with Android, version 4.3 and newer - most devices manufactured from 2012. Thanks to this function we can easily increase their memory capacity, or easily transfer photos and other data.