“The intuitive sensation of “being” in an environment, real or virtual, which results from the capacity to carry out one’s intentions within that environment. In other words, because of presence, an individual is able to situate himself in a physical and social space by defining his own boundaries.” — Networked Flow, A.Gaggioloi et al
There are certainly more mystical ways of looking at what presence is, but that one works well, also academically. Think about virtual reality, telepresence robots, or just about any electronic way of “meeting” people, or of exploring and learning subjects, or even any presentation of a story. What makes one feel that one actually is there? It is not necessarily the quality of the picture, and it might work even without any picture. You’re not present just because you can see something really well.
You’re present in a space, in a reality of some kind, if you can do something that you’d like to do, carry out some kind of action, and you can sense that it happened. I.e. there’s some kind of perceptual feedback.
On top of that, social presence is when there are others present, and you can sense actions they carry out, and there’s some kind of interaction.
To greatly simplify and summarize: most everything desirable is better when one can be more present with it or in it.
If one is present, one is more engaged, one is paying better attention, one learns better, what one does is more meaningful.