A primary source is an original object or document created at the time under study that offers direct, firsthand information about the topic. Examples include historical documents, artworks, eyewitness accounts, published results of experiments, and statistical data. A secondary source is a work created later that interprets, comments on, or builds upon primary sources, such as journal articles, books, documentaries, or textbooks. When evaluating sources, it is important to consider an author's perspective, potential biases, and whether conclusions are based on multiple sources or a single piece of evidence.