If you own Google Nexus 4, you may already Know that Google Nexus 4 has no OTG support which means that you cannot connect a usb device to Nexus 4 using a OTG cable or use a bigger storage device along with your Nexus 4 using a USB cable.
Looks like Google has changed this for recently released Nexus 5. Nexus 5 it seems supports OTG and hence can be used to connect usb devices or storage media with Nexus 5 using OTG cable. Checkout one of the screenshots below which shows USB hosts and OTG support.
With OTG support, you can connect an USB stick, usb keyboard, usb mouse or even DSLR Camera. A short demonstration video with Canon DSLR Controller on the Nexus 5 is shown in the Youtube video where canon DSLR is controlled using Google Nexus 5.
OTG support is definitely one feature that many advance users like us missed in Nexus 4 and hence it may be one more reason for many users to upgrade from Nexus 4 to Nexus 5.
Source : Reddit