Social media marketing refers to the process of gaining traffic or attention through social media sites.
Social media itself is a catch-all term for sites that may provide radically different social actions.
Social media often feeds into the discovery of new content such as news stories, and 'discovery' is a search activity. Social media can also help build links that in turn support into SEO efforts. Many people also perform searches at social media sites to find social media content. Social connections may also impact the relevancy of some search results, either within a social media network or at a 'mainstream' search engine.