From IFWiki

A term describing a work of interactive fiction that emphasizes traditional literary characteristics (plot, character, dialogue, etc.) The designer of such a game wanted to tell a story, rather than create devious puzzles to give the player's brains a workout.

Individual games typically fall fairly clearly on one or the other side of the puzzle/plot fence. There are exceptions, though. (SietseBrouwer, can you think of any examples? --DGJ)

Because pacing is essential to a good story, writers usually try to limit the number of turns a player hangs around hugging trees. To enforce this, the game is usually divided into a number of sections. Once a player has reached the next section, he cannot go back to the previous one. As sections tend to be small, players can examine everything and then move along fairly quickly. Or a simple puzzle is incorporated into the section, the player will fix his attention on the puzzle and try to solve it, and presto! he is moved on.

-- SietseBrouwer - 22 Nov 2002