A campaign is different from a direct request, because it can be reposted by multiple members. Campaigns are created by selecting a track or playlist, choosing a credit budget, and configuring who is able to repost it.
Once a campaign is live, it is posted on the Campaigns page and all members are able to listen to the track and repost it if they like it. Each repost will take credits out of the budget until there are none left, at which point the campaign will end.
The number of credits deducted from your budget when your track is reposted will depend on how many genuine followers the reposter has.
Campaigns will also end after 7 days. Any credits remaining in the budget are refunded to the campaign creator.