These are the familiar Virtual Reality goggles. He wrote what might be the best computer program of all time, Sketchpad, in 1963. It was the first computer graphics application. You could draw directly on the screen with a lightpen, and could modify the program with a graphical programming language. The problem was you couldn't see enough at one time.
Screen space becomes cluttered and then runs out almost instantly.
So Ivan imagined an ultimate display that could allow the user to move about through a potentially infinite virtual world instead of a real screen with hard boundaries. Ivan, a card-carrying nerd, drew his terminology from the metaphors popular in the sciences at the time. If it were always indistinguishable, there would be identity, rather than virtuality. It turns out that the two words, virtual reality, had appeared in that sequence before I coined the term. The earliest example I have found is from French surrealist Antonin Artaud, who described effective theater as creating a virtual reality of the scenario being depicted.