Two versions of the Apple Watch: One, works only with WiFi/Bluetooth. The other, has a cellular connection. If you get the WiFi/Bluetooth version, it will work as a watch and fitness tracker. Other functions, such as walkie talkie, phone, messages, email, etc. require that your iPhone be close by. With this version, you do not need to contract for a cellular connection. If you get the cellular version, it will operate over a cell network without the phone being close by, but you have the monthly expense for the cellular connection.