Facebook is a social media platform launched in 2004. As of 2017 it has 17 billion active users. Facebook also owns Instagram, an image sharing social network. It also makes up the majority of the display ad market in the US.
Facebook is a crucial and necessary (almost everyone expects a business to have a Facebook page) marketing channel for businesses. Posting and sharing on Facebook helps branding as well as customer service and promotion. Optimizing your Facebook profile will help control more results on SERPs for your branded keywords.