USB OTG or USB On-The-Go lets you connect usb sticks / disks to some android devices such as the google moto g but not the asus nexus 7
http://en.wikipedia.org/wiki/USB_On-The-Go
http://www.cnet.com/uk/how-to/how-to-tell-if-your-android-phone-or-tablet-supports-usb-on-the-go/
Motorola Moto G Single SIM 16GB Sim Free Smartphone