Sources are the origins of information, data, or ideas. They can include books, articles, websites, interviews, and other materials that provide evidence or support for a claim. Reliable sources are essential for research, as they help ensure the accuracy and credibility of the information presented. In academic and professional settings, sources are often categorized as primary or secondary. Primary sources, like original research or firsthand accounts, offer direct evidence. Secondary sources, such as textbooks or review articles, analyze or interpret primary data. Properly citing sources is crucial to avoid plagiarism and to give credit to the original authors.