Immersive video is video that surrounds the viewer or responds to them. The term covers two things that behave quite differently: 360-degree footage the viewer looks around inside, and interactive video where their choices change what plays next.
The second is the one with a business case outside entertainment. When the viewer is choosing, every session produces a record of what they chose, so the video becomes a data-collection surface and a personalisation engine rather than a broadcast.
The caveat for 360 is that it demands attention most viewers will not give. It needs a headset or continuous dragging to see anything, and on a phone, watched once, most viewers never look behind them, so the expensive half of the production is never seen.
The blog goes further into where immersive formats are heading.