The technological advancement in recent decades blurs the line between the digital world and the real world, to the point that in the near future we will not be able to differentiate between the two. In less than a decade, XR's (extended reality) promising technology, transforms entire industries and becomes one of the building blocks of the Industry 4.0 revolution. In this lecture. we will review the technology in various products such as VR, AR, and MR. We will take a look at the differences between them and learn how the different industries use XR technology for their different needs.