There's a lot of lingo around the wider web (which is itself lingo) so this is one of a series of short definition posts.
Immersive displays include opaque head mounted displays like current virtual reality systems, see-through xrglasses, projection domes and CAVES, and any other display that surrounds you and gives you a view into a real and/or virtual environment.
"Immersive display" is a less specific term than "xrglasses", which are only see-through and only head-worn.
Immersive is one of the three display modes on the wider web:
Using Three.js to build a reusable border geometry for spatial UIs!
🌸 Updated potassium style system (KSS), now with margins!
🌸 The path to the vNext
🌸 A couple of new spatial controls
🌸 A brief intro to the existing samples
🌸 Building UI components that work in flat, portal, and immersive display modes