Footnotes are notes placed at the bottom of a page in a book or document that provide additional information or references related to the text. They help clarify points, offer citations, or give extra context without interrupting the flow of the main content. This allows readers to explore topics more deeply if they choose. Typically marked by a small number or symbol in the text, footnotes can include explanations, sources, or comments. They are commonly used in academic writing, such as research papers and articles, to support claims and give credit to original ideas or works, like those of scholars or authors.