The document summarizes several media theories including the hypodermic needle theory, two-step flow theory, uses and gratification theory, reception theory, structuralism theories from Todorov, Levi-Strauss and Propp, participatory culture theories from Leadbeater, Anderson and Jenkins, and Web 2.0 theories on the changing nature of online participation and content creation. Key ideas covered include the influence of media on audiences, the role of opinion leaders, active audience choices, encoding and decoding of messages, narrative patterns, and the democratization of media through user-generated content and networking effects online.