How does the 4g prepaid usb nic work?

There is a 4g net stick you can get at Walmart and best buy that connects to a cell phone company satellite or something...

What I want to know and cant seem to get the information because its like a secret or something... IS...

When I connect to the internet using one of these cell phone signal powered cards what is going on?

Does the card have a unique id that will always be present when connecting? So say for example that I accidentally stumbled into some child pornography... (This is simply a bad example). I am put onto a watch list by the department of defense. Would they simply need to have a list of connections using wireless nic cards and then when I connect they would see the unique ID?

I'm hoping that I can use it and not be linked to a unique ID... But it seems that what you hope for never happens these days...