Field of view
A field of view is an area that can be seen by the eye. It is a visual space. It is the observable visual extent of a view. It is the space on the retina that is taken by something. Its spatial extent can be measured approximately using an angular measurement, for example using degrees.
The field of view of a normal computer screen is approximately the center third of the vision. Either desktop or laptop.
Head mounted displays[edit]
Virtual reality headsets typically have a field of view of at least 90 degrees. The higher an HMD's FOV is, the further the virtual world will extend to your edge of vision, also known as the visual periphery.
The field of view of a head mounted display needs to be higher than a world-fixed screen to be comfortable. This is because when you turn your head with a headset, the content stays fixed in the world and gets cut off at the sides in your periphery. This is highly noticable with the Magic leap 1 and Hololens 1.