A social media campaign is pretty much what the name says, it is for social media, which includes, but is not limited to, Facebook, twitter, telegram and Instagram. Some campaigns will pay you for doing certain activities on those social media campaigns, like say following their ICO page, or tweeting about them if you have a lot of followers. Social media campaigns usually don't pay as much as signature campaigns, since social media campaigns require less work, and if you have barely any followers on social media, they will pay like a dollar for posting something. If you are looking for ways to make money, I would recommend leveling up your account to full member and then enrolling in some signature campaigns, or becoming a freelancer and looking for odd jobs.