This document summarizes key aspects of social communities from a chapter in a textbook. It discusses how individuals create digital profiles to participate in social communities. It also describes presence indicators that allow users to project themselves, such as availability icons, mood icons, friend lists, and status updates. The document outlines different types of social interactions on these communities, including direct private messages and passive consumption of content. It also examines characteristics of social networking sites, such as their target audience, the social objects that mediate relationships, and their degree of openness. Finally, it discusses how marketers can use social communities for paid media, earned media through engagement, and user-generated content campaigns.