What is cellular network data?

I just got an iPhone through Verizon and when I go into usage there's a thing that says cellular network data and it just keeps going up and up but I don't understand why. I don't use Internet outside of Wi-Fi ever. I don't even know what cellular network data is. Someone explain?

When a Wi-Fi network is unavailable, iPhones are capable of using a cellular data network for Internet connectivity.

If you don't use the internet outside of Wi-Fi then you have nothing to worry about. But say for instance you are streaming YouTube videos on your phone and you are not connected to Wi-Fi, you would be using celluar data as part of your data plan you got with Verizon. I'm not sure what kind of data plan you have (I have 2gb), but make sure you don't go over that usage limit or they will charge you.

They used to sell "unlimited data plans", but I think that is no longer available with most cell phone companies.