The main types are augmented (using your device [looking through the screen] typically overlaying a 3D model appearing on top of the image) and virtual reality are the main types.
SandboxAR has introduced a feature to bring a hybrid approach that allows you to scale up the augmented reality and use your device as a "magic window" and share the experience with others.
Sound is important because it helps create and amplify the atmosphere of the enironment you are exploring.