The first of the Uni-related links.
(Tele-)Presence is the "subjective experience of 'being there' in mediated environments such as virtual reality, simulators, cinema, television, etc."
It's fascinating stuff, especially in the field of designing for interactivity and immersion.
In particular, Lombard & Ditton's "At The Heart Of It All - The Concept of Presence" is worth a read.
Based on this stuff, one of my assignments this semester involved creating a purpose built room for enhancing presence in Horror based Role Playing Games.