Gamasutra - In game development you'll need to

write a game plot summary. Alexander Freed shares his thoughts on thisin a blogpost at Gamasutra.   A quote on what a plot summary is:

A plot summary (or a synopsis, or a narrative outline-call it what you will) is a prose recounting of a game's story, narrating the major events and character beats. It is not a technical document; while it may (or may not) break down the story into clear gameplay elements, suggest asset requirements, and so forth, its emphasis is on telling a story

A quote on who this plot summary is for:

For team members without a direct stake in the particulars of the narrative (e.g., a tools engineer or a QA project manager), a plot summary serves as a useful reference doc to help communicate one aspect of the overall project vision; it's always good for people to understand and be enthusiastic about what they're creating, and a clear, concise, engaging plot summary document will help generate excitement. For team members with a strong direct stake in the narrative particulars, however, a summary doc is even more important. It serves as the first line of defense against unexpected problems and misunderstandings.

An example and the quote for it:

 Example: The Player confronts the warlord and, either diplomatically or through threats and blackmail, learns the location of the downed helicopter and the UN medical supplies. The warlord warns the Player that the guerillas have likely already picked the wreckage clean, but it's unclear whether he's telling the truth.

Why handle the plot summary this way? It certainly makes writing one more difficult, but the summary isn't just meant to tell a story-it's meant to represent the actual game narrative experience. If you're not telling it from the Player's point of view, you're telling a different story altogether and there's no way to be sure whether the game's narrative will hold together. There's no way for others to judge what needs to be built for the game.