Short answers, pulled from the story.
The very first standalone Dungeons and Dragons adventure module was created by a small publisher called Wee Warriors. In 1976, they released Palace of the Vampire Queen, which Wizards of the Coast distributed for the first three printings.
TSR published Steading of the Hill Giant Chief in 1978 as the first stand-alone Dungeons and Dragons module actually produced and published by the company. This module had previously been used only in tournaments at Origins 78 before its commercial release.
Early Dungeons and Dragons adventure modules were single booklets inserted but not fixed inside a cardboard cover. This design reflected the makeshift nature of the hobby at the time before evolving into complex spiral-bound notebooks.
TSR dropped the alphanumeric coding system for Dungeons and Dragons modules altogether by the end of 1993. The code was reintroduced in 2008 with the release of the 4th edition Dungeons and Dragons adventure H1 Keep on the Shadowfell.
Early editions of the game commonly referred to these publications as modules, which stems from the term dungeon module used to refer to the earliest adventures published by TSR. The term adventure is currently used by the game's publisher Wizards of the Coast, while the term module continued to be popular among players of the original Dungeons and Dragons and Advanced Dungeons and Dragons.