Paid media: The social ads you invest in so that they are displayed to predefined audiences.
Owned media: Content posted on a brand's social channels, your Twitter profile or corporate LinkedIn page. Marketers measuring the success of owned media will often look at the engagement rate.
Earned media: User generated content involving a brand, but which the brand has no control over. More often than not, earned media is the result of carefully planned paid and owned media campaigns.