USB On-The-Go allows USB devices such as tablets &mobile phones to act as a host allowing a USB Flash Drive, mouse, or keyboard to be attached. USB On-The-Go (OTG) allows two USB devices to talk to each other without requiring the services of a personal computer (PC). For instance, this implies that you can access your USB flash drive directly on your mobile phone/tablet.
Popular Compatible Device (Just a summary):
A+ 7'' Tablet - All Versions
Google: Nexus 5 / 6 / 7 / 9 / 10
Samsung: Galaxy S2 S3 S4 S5 Note 2 3 | Galaxy Note 8.0 Galaxy Note 10.1 2014 Edition | Galaxy Tab 3 8.0 10.1 | Galaxy Note pro 12.2, Tab pro 12.2 / 10.1 / 8.4 | Galaxy Tab S 8.4 / 10.5 / 13.3
Motorola: Moto G Phone | Xoom Tablet
HTC: HTC One M7 M8
Nokia: Lumia 2520 Tablet | Nokia 603 | Asha 300 | C6-01 | C7 E6 E7 | N8
Toshiba: TG01 | encore
Tesco: HUDL 7" plus
Acer: Iconia B1-720 | B1-730 HD | A1-830 | A1-840 FHD A1-810 | W3-810 | Memo Pad HD 7 / 10
Lenovo: Thinkpad 8 | IdeaTab A7-40, A7-30, A8-50, A10-7
LG: G3 G Pad 8.3 7.0 8.0 10.1
Sony: Xperia Z2 Miro/U/S/T/M/M2/SP/P/Z/Z1/Compact/Z2/Ultra/Z
Dell: Venue 7 / 8 / 8 Pro.