The exact process of experiencing a campaign's content depends on the gameplay mode being played, with some modes utilising single chapters of a campaign for each game rather than progressing from one chapter to the next.
Chapters are typically played in order, following a narrative in which the Survivors travel from a start point in the midst of the zombie apocalypse to an end point where a rescue vehicle to safety awaits, surviving the onslaught of the Infected as they go. Campaigns are aesthetically presented as if they are individual zombie movies, complete with a poster on the loading screen for each one, and usually consist of several chapters (also referred to as 'levels' or 'maps'). Campaigns (or movies) are grouped sets of environments used for gameplay in Left 4 Dead and Left 4 Dead 2.
