FaceTime is Apple's video and audio calling service. Think of it as a phone that uses your Wi-Fi or cellular data connection instead of traditional phone lines. You can use it from any iPhone, iPad, iPod touch or Mac, to call anyone else using any one of those devices.
Skype is a telecommunications application that specializes in providing video chat and voice calls between computers, tablets, mobile devices, the Xbox One console, and smartwatches over the Internet. Skype also provides instant messaging services. Users may transmit text, video, audio and images.
Here are several ways (with video tutorials) on how to communicate via the internet.