I saw a question on Twitter today asking how long a campaign lasts. That got me to thinking and depending one your RPG experience and preferences, the term campaign has multiple meanings.
Campaign comes to RPGs from tabletop miniature wargaming, which in turn gets the term from military parlance. The military use of the term derives from the plain of Campania, a place of annual wartime operations by the armies of the Roman Republic.  Generally, a campaign is a specific portion of a war, such as a series of battles or specific strategy. It can also be a region/terrain, such as the desert campaign in WWII.
The various shades of meaning in relation to RPG’s that come to mind are: (This is in the context of D&D in my mind, substitute your primary RPG of choice.)
- The entire game world/multiverse and all activity happening under a DM. That is, the campaign setting.
- A specific connected set of adventures/game sessions with a clear end point. Often this means the end of that game “world”, and after a break a new world emerges.
- An example from published modules would be the Drow series.
- A campaign in a DM’s ongoing world might mean a major event in the world is resolved, or it might mean players have reached a level where retirement is in order and a new batch of characters enter the realm.
- A specific group of players and their characters. It may be that circumstances prevent that group from playing again, and the end of the campaign is the end of regular play among that group of people.
- A DM with a single campaign setting can encompass multiple groups of players and each could be their own campaign, or they could be somehow interconnected. There are lots of examples of DMs running the same setting for decades.
When campaign is used to refer to the setting, it can be a single genre, multiple genres, homebrew, or published.
In a multi-genre campaign setting, one could have D&D set in the past, then western/steampunk, then modern, then apocalyptic, then future. The order could be different, such as in Jack Vance’s far future world where there is magic.
Other GMs have a separate setting for each genre. They could even mix and match home brew for one setting and a published setting for another.
A DM can even have a campaign to get the word out that they are looking for new players.
There can even be a campaign of war within the RPG itself.
So a DM can campaign for new players for their campaign setting that features military campaigns in the game.
What does the term campaign in the context of table top RPGs bring to mind for you?