If you were to head on over Apple’s online store, you will be able to select the SIM-Free option. For those who are unfamiliar with SIM-free devices, Apple write, “The SIM-free iPhone comes without a wireless contract commitment or carrier financing. It doesn’t come with a nano-SIM card for iPhone 6s, iPhone 6s Plus, iPhone 6, iPhone 6 Plus, or iPhone 5s. And because it’s unlocked, it isn’t tied to one carrier, so you can get a nano-SIM from any supported carrier worldwide, such as AT&T, T-Mobile, Verizon, or Sprint in the United States.”
Basically this is just the iPhone and the iPhone alone at its full retail price. If you wish to use it as an actual phone, you will have to get a SIM card from a carrier. However given that it is unlocked, it means users get to pick and choose whichever carrier they want. It is ideal if you hate being tied-down to contracts, and if you plan on traveling a lot and want the freedom to insert foreign SIM cards into the phone.