The following is text from the "GURPS Basic Set, third edition (copyright 1991). This is selected text which reveals the authors' view of what roleplaying is and the responsibilities of GM and players.
"WHAT IS ROLEPLAYING?" Section, page 8
A roleplaying game is a game in which each player takes the part of a "character", participating in a fictional adventure. The nature of the adventure is set by the referee, called the Game Master (GM, for short). The GM determines the background and players the part of the other people the characters meet during their adventure.
No gameboard is necessary for a roleplaying game (though some systems, including GURPS, include optional "boardgame" rules for combat situations). Instead, the game is played verbally. The GM describes the situation, and tells the players what their characters see and hear. The players then describe what they are doing to meet the challenge. The GM describes the results of these actions . . . and so on. Depending on the situation the GM may determine what happens arbitrarily (for the best possible story), or by referring to specific game rules (to decide what is realistically possible), or by rolling dice (to give an interesting random result).
Part of the object of a roleplaying game is to have each player meet the situation as the character would. A roleplaying game can let a player take the part of a stern Japanese samurai, a medieval jester, a wise priest, a stowaway gutter kid on her first star-trip . . . or absolutely anyone else. In a given situation, all those characters would react differently. And that's what roleplaying is about!
Thus, good roleplaying teaches cooperation among the players, and broadens their viewpoints. But it's not purely educational. It's also one of the most creative possible entertainments. The major difference between roleplaying and other types of entertainment is this: Most entertainment is passive. The audience just sits and watches, without taking part in the creative process.
But in roleplaying, the "audience" joins in the creation. While the GM is the chief storyteller, the players are responsible for creating their own characters. And if they want something to happen in the story, they make it happen, because they're in the story.
So, while other types of media are mass-produced to please the widest possible audience, each roleplaying adventure is an individual gem, crafted by the people who take part in it. The GM (or the original adventure author) provides the raw material . . . but the final polish comes from the players themselves.
The other important thing about roleplaying is this: It doesn't have to be competitive. In most roleplaying situations, the party will succeed or fail as a group, depending on how well they cooperate. And, just as in real life, the most important rewards of good roleplaying come in character development. The more successfully a player portrays his character (as judged by the GM) the more that character will gain in ability.
A roleplaying adventure may have a fixed objective . . . save the Princess, find the treasure, stop the invasion. Or it may be open-ended, as the characters move from one escapade to the next. It's all up to the GM and the players. A roleplaying "campaign" can be open-ended, lasting for years, as characters (and players) come and go.
When it's all said and done, the GM and the players will have crafted a story . . . the story of how the characters met, learned to work together, encountered a challenge, and (we hope) triumphed!
"GAME MASTERING" Chapter, page 177
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