FaceTime is the ultimate video chatting app that allows you to stay connected with your friends and family from anywhere in the world. With FaceTime, you can make high-quality video and audio calls, share photos, and even play games with your contacts.
From Wikipedia
FaceTime is a proprietary videotelephony product developed by Apple. FaceTime is available on supported iOS mobile devices running iOS 4 and later and Mac computers that run Mac OS X 10.6.6 and later. FaceTime supports any iOS device with a forward-facing camera and any Mac computer equipped with a FaceTime Camera. FaceTime Audio, an audio-only version, is available on any iOS device that supports iOS 7 or newer, and any Mac with a forward-facing camera running OS X 10.9.2 and later.