From TM Wiki

In TrackMania a campaign is a series of tracks grouped together for playing.

Campaigns are made of several groups of tracks. Tracks in later groups can only be played if you have won medals in the previous group.

Campaign Menu in TrackMania United Forever

All games of the series come with a built-in campaign from Nadeo, which forms the single player mode. TrackMania Sunrise also supports building custom campaigns. Also in TrackMania Sunrise you can win cups by finishing a whole campaign with the same medal, i.e. you win the silver cup if you win the silver medal on all tracks of the campaign. In TrackMania Nations ESWC cups are simply called ranking.

Campaign Menu in TrackMania Nations ESWC

In September 2008 Nadeo came up again with something new: The StarTrack Contest. This was a one off event, hosted with Nadeo using TMX as a platform and TrackMania United Forever as the game. Those registered for this contest used TMU-Forever to make new tracks that appear in a special community campaign to be available to all owners of TMU-Forever as an automatic download.