In the Dungeons & Dragons role-playing game, adventure or module is a term for pre-packaged books or box sets that help the Dungeon Master to manage the plot or story of a game. The term adventure is currently the preferred term.
In early editions of the game these publications were commonly referred to as modules, which stems from the term dungeon module, used to refer to the earliest adventures published by TSR, with other variations on the module name appearing on latter adventures. The term module continued to be popular among players of the original Dungeons & Dragons and Advanced Dungeons & Dragons even after newer publications were labeled adventure. Adventures that appear as a part of a larger accessory are often referred to as scenarios.
The exact differences between the terms adventure, module, scenario, and accessory are hard to precisely define in Dungeons & Dragons terminology, as they all have been used in different ways.
The first stand-alone Dungeons & Dragons adventure module, Palace of the Vampire Queen, was published in 1976 by Wee Warriors. Although TSR did not produce this module, the company did distribute the first three printings on behalf of Wee Warriors. The adventure was described as a "Dungeon Masters Kit" rather than a "module" or an "adventure."
Also in 1976, the adventure Lost Caverns of Tsojconth was distributed by Metro Detroit Gamers as the tournament module for the gaming convention Wintercon V, but was not published for general distribution at the time. The adventure was later re-written for the first edition Advanced Dungeons & Dragons rules and published as module S4 - The Lost Caverns of Tsojcanth (TSR, 1982).
Additional unpublished adventures were distributed at gaming conventions during this period, including Steading of the Hill Giant Chief, used as a tournament module for Origins '78. Later in 1978, Steading of the Hill Giant Chief became the first stand-alone Dungeons & Dragons module actually produced and published by TSR. The company initiated its practice of assigning a code to each module published at the time, assigning the "G1" code to Steading of the Hill Giant Chief. TSR's practice of coding modules into various series would continue into the 1990's.
Modules had a suggested character level, often displayed prominently on the cover, and from the late 1980's prominently display the logo of the campaign setting they were set in. Some modules were reprints or revisions of modules used at gaming conventions before being published. All early modules are now out of print, though some have been reprinted in revised form. As such, many early modules are now highly sought-out collector items, particularly the earliest printings.
TSR also used the module coding system on modules for several of non-Dungeons & Dragons roleplaying games including modules for (Advanced) Marvel Super-Heroes and the Conan Roleplaying Game. The module code was de-emphasised in the late 1980s, which also saw the campaign setting logo become a main feature of the cover. The code was dropped altogether by the end of 1993.