This document provides an overview of different types of advocacy groups in the United States. It explains that groups like 501(c) organizations, 527 groups, political action committees (PACs), and super PACs all have different rules set by Congress and the FEC regarding how they can raise and spend money to influence politics. The document gives examples of prominent groups that fall under each category and directs readers to the website OpenSecrets.org for more information on different groups and their financial activities.