- The Game Master (GM) briefs the players on the situation.
- The Game Master fields relevant questions and reminds them of resources at their disposal.
- The Game Master asks the players what their characters do.
- The Game Master administers the chosen actions, adjudicates the results, and announces results to the players.
- The Game Master updates the situation, and the loop repeats.
The ability to stick to this one feedback loop, in the hands of an average man, allowed gameplay to go from searching ruins for treasure to travel across the stars to dealing with court intrigue--all with the same characters in the same campaign--without needing to switch entire games or rely on external content producers. Content could be produced more or less on the fly, entirely local, and entirely suited to the specific individuals that consumed it.
Specific subsystems built upon this feedback loop, notably the combat systems, but those that worked best kept formal systems to only what was required and left the rest to the GM to rule as he saw fit. The GM is the load-bearing pillar for the medium. A man who is knowledgable, well-read, etc. and confident will recognize the value of this feedback loop and rely upon it to play to the medium's strengths. He will reliably produce a compelling and entertaining campaign experience for players at his table as a result.
This loop means that this is not about telling stories. It's about solving problems, as one expects from a medium derived from wargaming, and as such it is a medium that is about testing player skill first and foremost. The use of a secondary persona is meant as a handicap, forcing the player to deal with deficits that otherwise are not present as well as granting resources otherwise unavailable.
A proper tabletop RPG, therefore, is not a spectator-friendly affair. It is deeply personal, irrelevant to those not there participating in the events at hand, and often not fun to watch if you're not already curious about how the medium works to produce satisfying gameplay experiences.
What those experiences are is another post.