A typical Dungeons & Dragons game consists of an 'adventure', which is roughly equivalent to a single story.[48] The DM can either design an adventure on his or her own, or follow one of the many additional pre-made adventures (previously known as "modules") that have been published throughout the history of Dungeons & Dragons. Published adventures typically include a background story, illustrations, maps and goals for PCs to achieve. Some also include location descriptions and handouts. Although a small adventure entitled 'Temple of the Frog' was included in the Blackmoor rules supplement in 1975,[49] the first stand-alone D&D module published by TSR was 1978’s Steading of the Hill Giant Chief, written by Gygax.[50]

A linked series of adventures is commonly referred to as a 'campaign'.[51] The locations where these adventures occur, such as a city, country, planet or an entire fictional universe, are also sometimes called 'campaigns' but are more correctly referred to as 'worlds' or 'campaign settings'.[52] D&D settings are based in various fantasy subgenres and feature varying levels of magic and technology.[53] Popular commercially published campaign settings for Dungeons & Dragons include Greyhawk, Dragonlance, Forgotten Realms, Mystara, Spelljammer, Ravenloft, Dark Sun, Planescape, Birthright and Eberron.[54] Alternatively, DMs may develop their own fictional worlds to use as campaign settings.

Taken from Wikipedia