This document discusses virtual reality (VR), including its history, types, technologies, architecture, applications, advantages, and disadvantages. VR creates the illusion of a 3D interactive computer-generated environment and can immerse users in virtual worlds through head-mounted displays and other technologies. Some examples of VR applications mentioned are entertainment, education/training, games, and biological/medical uses like practicing surgeries. While VR enables new experiences, it also has disadvantages like high equipment costs and the inability to move naturally like in the real world.