The following information is from Wikipedia.com and was uploaded February 19th, 2009.  This is a great start to understanding Social Media Marketing.  

''Social media marketing'' is a set of online marketing techniques that leverage social media. In the context of Internet marketing, Social Media refers to a collective group of web properties whose content is primarily published by users, not direct employees of the property (e.g. the vast majority of video on YouTube is published by non-YouTube employees). Social media optimization (SMO) is a set of methods for generating publicity through social media, online communities and community websites

Social media marketing has two important aspects. The first, SMO, refers to on-page tactics through which a webmaster can improve a website for the age of social media. Such optimization includes adding links to services such as Digg, Reddit and Del.icio.us so that their pages can be easily 'saved and submitted' to and for these services.

Social media marketing, on the other hand, is about building ways that fans of a brand or company can promote it themselves in multiple online social media venues.

Some social media marketers offer to write content that is remarkable, unique, and newsworthy. This content can then be marketed by popularizing it or even by creating a “viral” video on YouTube and other video sites, including getting involved in blogs, forums, and niche communities.

According to Lloyd Salmons, first chairman of the Internet Advertising Bureau social media council  "Social media isn't just about big networks like Facebook and MySpace, it's about brands having conversations".  In fact, most individuals who study the space believe social media is about people having conversations, not brands.

What is NOT Social Media Marketing

It is important to highlight in social media's case of what is does not stand for. Most individuals confuse it with advertising on social networking sites. It is anything but that. Advertising that appears on these social networking sites is more in the form of context or social action based. Networks monitor what the users are doing and place relevant ads next to them with the assumption that they will be clicked.

Social Media Marketing is not about spamming. It is not about copying certain links and spamming it in discussion groups and forums. It is important to create value for the people with whom you are dialoguing.

Social Media Marketing is all about collaboration between people. It is about participating with everyone and sharing information. It is as much about giving as it is about receiving from the group. The premise of social media marketing is engaging with the consumer and providing value. It is important to maintain the sanctity of conversational economy.