Apple's FaceTime is a chat application for Apple computers, iPhones, iPads and iPod touch devices that allows users of these devices to video chat with users of other Apple devices. Skype, on the other hand, is a messenger that isn't specific to any computer operating system. Although it is possible to use Skype on Apple computers, it is neither possible nor necessary to use FaceTime in conjunction with Skype.
To use FaceTime, you and the individual with whom you want to connect must both be using Apple devices. In addition, any party that wishes for the other to see a live video feed of his face must be using a device with a working webcam. If you don't need the other person to see you, it's possible to make a voice-only FaceTime call to him, although you can see him if his computer has a working webcam.
FaceTime for iOS Devices
It's possible to use FaceTime to make calls using devices the employ the iOS operating system, such as the iPhone, iPad and iPod touch. If you attempt to call another iOS device user via FaceTime using the iPhone, you must connect to a nearby Wi-Fi connection. As of October 2011, it isn't possible to make a FaceTime phone call to another user while connected to the Internet via a cellular data plan.
Adding FaceTime Contacts in Skype
Because Skype and FaceTime are separate programs, it isn't possible to make a FaceTime video or voice call via Skype. One way to use Skype to communicate with FaceTime contacts is to add them to your Skype buddy list. To do this, select "Add Contact" and type in the person's name, email address or Skype username.
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Skype Video Chat on iOS Devices
It's also possible to use Skype to make video calls on certain iOS devices -- namely, the iPad, the Phone 4 and 4s, and fourth-generating and later iPod Touch devices. If your device has a front-facing camera and the latest version of Skype, it's possible to make video calls using it and unlike with FaceTime, you need not be connected to Wi-Fi when making a video call using the iPhone. If your device doesn't have a front-facing camera, you can still receive video calls via Skype on an iOS device.