Chatd is a tool that enables users to engage in textual conversations with their documents through a private local AI. By downloading it on Mac, users can request document summaries and ask questions about the content. In the given example, the tool is used to summarize information about the solar system, specifically its formation around 4.6 billion years ago. Chatd Logo streamlines the process of extracting and interacting with textual data from your computer, offering a convenient way to access and query information within your documents using natural language communication.