What does FaceTime mean?
FaceTime is a video chat application developed by Apple and supported by devices such as iPhone4 and above, 4th generation iPod touch or above, iPad2 or above running on Apple iOS and Macintosh computers that run Mac OS X 10.6.6 or above. Making use of front-facing and rear-facing cameras in the devices, it was initially available only on Wi-Fi connections, but was made available over mobile networks as well for iPhones. FaceTime allows Apple users to make free calls to other Apple users over a cellular connection or Wi-Fi.
Techopedia explains FaceTime
FaceTime allows only connections between Apple devices and supports only one-to-one video services. It is highly incompatible with non-Apple devices or with other video calling applications and services. Although in iPhone FaceTime is bundled into phone applications, it is a separate application for all other Apple devices like Mac, iPad or iPod touch. As a dialer is absent in these devices, an Apple ID and an email ID are required for FaceTime on Mac, iPad and iPod touch.
FaceTime calls are protected by end-to-end encryption, resulting in access restricted to only the sender and receiver. FaceTime restricts the usage of other applications while in use, and thus encourages both callers to be fully attentive while conversing and not distracted by other forms of communication or technology applications.
By taking advantage of the dual cameras present in devices such as iPhone and iPod touch, FaceTime supports video conferencing. FaceTime allows convenient switching between the front-facing and rear-facing cameras while in use. Unlike other video chat applications, FaceTime does not require the receiver to be online. The behavior is similar to dialing a phone number. Another benefit of using FaceTime is that it does not need the FaceTime client to be running on the receiving side in order to receive the call. This feature helps in saving battery usage.
FaceTime Audio was introduced in iOS7 which allowed FaceTime users to decide between audio only calls or video calls.