RPGs are games of information and choice.
...players at the game table need to be able make informed decisions or their choices are meaningless. If the players are in a wilderness hex crawl with 6 directions to travel, they might as well roll a 6-sided die to choose - unless the referee is supplying them with enough information to weight the options. That's where the game is at, that's where the fun is - the exercise of meaningful choice and then handling the consequences. (Dreams in the Lich House)
The most important point of this post is this cartoon. If you don't want to read me spend several paragraphs thinking aloud for my own benefit, skip to the end.
Understanding RPGs as information games does bring in contrast my unease with games that have 'information gates' built into their mechanics. I play and enjoy those games. But I do think that it takes real GM skill to play a game that, by the book, is peppered with rolls that (in the hands of a bad GM at least), might deny players the information that required to make meaningful choices on behalf of their characters. Despite playing games with these kind of mechanics (WFRP, RQ etc.) I'm never sure whether I've managed to get the correct balance between information simply given, information supplied in response to player questions, and information granted by virtue of character abilities. I thought about something like this some time ago, suggesting that, despite spending a large amount of time away from D&D in favour of more 'realistic' games (and an even longer time not playing at all), my experience with the particular iteration of the 'Information Game' of D&D has baked-in the way I referee a game - I am a DM, not a Keeper.
But there is another aspect to the information game of RPGs that most 'how to play' sections miss; the fact that the information flow of the game is not one way. The GM needs to extract information from the players. I have found that players might be very good at providing statements of intent that accurately express the will of their character for the next 6 seconds/10 seconds/60 seconds (delete by edition). But they often keep their longer term goals - longer term here might mean their goals within a single encounter - obscure. Sometimes this is deliberate, when players feel they are playing against the referee, but often it is because the players have not really understood the fact that the information that they have of (encounter) situation is necessarily incomplete. The description of a situation can only by a few sentences long. This can be 'total information' in a boardgame in which there are only a limited number of options. The only information that is game relevant is that which directly impinges on the mechanics of the game. In a RPG, with 'tactical infinity' this is the merest skeleton of situation. Any information can be game relevant, depending on the imaginations of the players and the GM. Nothing can be dismissed a mere 'colour text'. Players can flesh out the information 'skeleton' by asking questions of the referee, but unless the referee knows the 'longer term' plans of the players and their characters, the referee cannot provide directly relevant information, nor can the players be assured that all the information relevant to their plans has been provided.
Along with necessarily incomplete information, the transmission of this information is almost certainly imperfect. Even in a totally railroaded game with boxed text producing perfectly homologous imaginations is not going to happen. Significantly divergent imaginations of the situation are more likely in games in which the referee generates encounters in play and improvises descriptions - i.e. a game that allows for significant player/character choice. Without players explaining the longer term plans of their characters, those plans will likely be frustrated by misunderstandings of the situation. Or the referee, not wanting to disappoint the player as his character's imaginative plan is revealed one action at a time (ending with a great reveal - 'Ta Dah!'), will shift the 'reality' of the game world to match the misunderstandings of the player. That's not a bad escape to the situation, socially, but in game terms it denies the importance of player/character choice as the 'reality' upon which they were acting had no solidity.
tl;dr: Players need to ask questions, but Referees need to question players over the intentions of their characters in order to ensure as close as possible a shared imagination of the game world.
Added bonus: NPCs with mind-reading skills (or high 'Spot Motive'/'Insight' etc. skills) can do their thing with ease!