Virtual reality places a screen in front of your eyes so that you only see a virtual 3D world. Augmented reality places a digital layer over reality and Mixed Reality places digital objects in reality.
With AR and MR, the device being used transmits a live image of real-world conditions which is then enriched with computer-generated output, such as sound, video, images or GPS data. In VR, this reality is completely created by the computer.
The purpose of these technologies is to add something to reality or to create a new digital reality for the purpose of insight, education or entertainment.