In journal articles, research papers, published patent applications and patents, an abstract is a short summary placed prior to the introduction, often with different line justification (blockquote) from the rest of the article, used to help readers determine the purpose of the paper. While the length of the abstract varies by field of study, it is typically a paragraph in length (3-5 sentences), and never more than a page. See
\url{en.wikipedia.org/wiki/Abstract(summary)} for details