iPhone 4S is the next logical step in the evolution of the iPhone 4.
When it comes to looks the iPhone 4S will have the same form factor as the iPhone 4 did.
The major changes include the device’s processor: now it features an A5 dual-core CPU (which was already used in iPad 2).
Apart of this the camera was much improved, allowing for genuine 1080P video capturing.
iPhone 4S will be able to work with both GSM and CDMA networks (reminder: iPhone 4 had different CDMA/GSM versions).
It will support HSDPA+ mobile networks, allowing for speeds of up to 14.4 mbit per second.
iPhone 4S will also feature new Siri technology, which allows for voice communication with the phone. For example it would allow you to ask your iPhone for the current temperature or to send an SMS using only voice controls.