Social media marketing refers to using social media platforms like Facebook, Instagram, and Twitter to market products and services. It allows companies to engage with customers, promote their brand, and reach new audiences. Some key points made in the document include: - Social media marketing grew out of early technologies like the telegraph and AOL in the 1990s and really took off with the creation of platforms like Facebook in 2004 and YouTube and Reddit in 2005. - Popular social media sites now include Facebook with 2.9 billion users, YouTube with 2.1 billion users, Twitter with 186 million users, and Instagram with over 1 billion users. - An estimated $50 billion will be generated from social media advertising in 2021