Social Media Marketing is a term that defines the idea of gaining traffic and attracting visitors for your page by using social media sites.
The social media term refers to all kinds of social networks and sites, each of them with its own particularities. While Twitter is a network where usually people post short updates and messages, Facebook is much more complex because it allows you to share with people a wider variety of activities, pleasures, messages, music videos etc.
The search tool is basically the most important when it comes to social sites. People search for other persons, for activities, for news stories and all kind of stuff to entertain them or make their lives easier. You may also find links to important SEO sites, articles and companies.