Sign USB Host and OTG, i've gone crazy!

From what i know,
OTG: A Port that can Be Both a client so it can be connected to PC and Host to Plug Some flash Drives, etc.
USB Host: They're just like the PC One's, They only Act as USB Host

However, Nexus 5, Supports Both USB OTG And USB Host..
I don't understand how? is there two USB ports one OTG and the other Host?
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