Is the cellular iPad Air compatible with other outside carrier or not?

Hey!

I have a friend currently in California and thought that he could buy the new iPad Air Wifi + Cellular but on the site I read following: "Your iPad will work only with the carrier you choose"

But later I see this: "iPad Air with Wi-Fi + Cellular can roam worldwide on GSM/UMTS networks. In countries without compatible LTE networks, iPad Air will operate on GSM network technologies such as HSPA+ and DC-HSDPA. When you travel internationally, you can use a nano-SIM card from a local carrier."

What do they mean with "you can use a nano-SIM card from a local carrier."

Will I be able to use my swdish SIM card with the iPad Air but not any other american carriers or what?

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via i42.tinypic.com


Thanks

Sebastian