What is a "West Marches" Campaign?

The most common format of D&D is the one most of us are familiar with – a few friends and a regular game master meeting on a semi-consistent basis to complete a greater campaign, quest, or story line. “West Marches” refers to a format of play popularized a while back where, instead of featuring a singular group or quest, players’ individual characters live and interact in designated social spaces with other players (at the time of writing this, we maintain a concurrent player base of about fifteen players, with even more who come and go at their leisure). Periodically, game masters – the people who run the game and everything in the game that isn’t a player – will organize quests, both short- and long-term, and off you go.
In this same vein, Chromatia does still feature a primary story line (see The Story So Far for a recap), coordinated by Chromatian Staff. The characters who contribute to progressing that story line may change from one quest to another depending on several factors.