This is a preface to various discussions of theoretical concepts in role-playing games. There is the valid question to ask what the point of it all is. Theorizing without purpose can be seen as pure ego-stroking -- attaching fancy-sounding names to something to make yourself seem important. Even though I see value in theory, I think it is good to keep that in mind.
To me, the primary goal of RPG theory should be to enhance communication among RPG players, critics, and designers. Too often, gamers find it impossible to discuss how games really work. If someone asks for advice on a specific problem of his game, she gets five contradictory answers on how to solve it. Discussion becomes mired in assumptions of a particular system, or paralyzed by stating only obvious generalities. I experienced both these over several years of discussion on the newsgroup rec.games.frp.advocacy.
To enable communication, theory needs to touch on important aspects of play, but it also needs to remain accessible to general gamers. In other fields, theories can be inaccessible to the public by having a community of specialized theorists. However, there is no Ivory Tower for RPGs. While communication with other fields can be useful, in practical terms if you want to talk about RPGs you have to talk to gamers.
Role-playing games encompass an enormous range. One game might be played using an online forum where players alternate posting short bits of fiction. Another game might be an event where 40 or more people gather in costume outdoors and roam about. Ideally, theory should provide a framework which allows a player in the former to exchange ideas with a player in the latter.
While some may find theory dry, it has happened that gamers have found explanation of essential concepts useful. Simply by expressing concepts, there are gamers who have found insight to improving their enjoyment of play. In particular, theory may cause a gamer to question assumptions.
This can be seen in particular in discussion on the web-based bulletin board The Forge, which is devoted to independent RPG design. There dozens of regulars have come up with game designs inspired by theory, and especially by questioning the assumptions of most commercial RPG designs.
One of the frequent problems of discussing RPGs is trying to relate them to other media such as novels, films, and other such. There is a constant struggle with metaphors. We talk about genre, plot, and other terms -- but they often have very different meaning from what they mean in those fields.