Spatial sound (or spatial audio) involves the manipulation of audio signals so they mimic acoustic behavior in the real world.
The human brain interprets audio signals in a specific way that allows it to make decisions about its surrounding environment. We use our two ears, in conjunction with the ability to move our heads in space, to make better decisions about the position of an audio signal and the environment the sound is in.
An accurate sonic representation of a virtual world is a way to create a compelling and immersive experience.
Spatial audio not only serves as a mechanism to complete the immersion but is also effective as a UI element: audio cues can call attention to various focal points in a narrative or draw the user into watching specific parts of a 360 video, for example.