An abstract is a short summary of a longer document that previews the paper's content and purpose. It follows an introduction-body-conclusion structure but in a more condensed form due to its limited length. The introduction states the paper's thesis and research question. The body covers the main ideas in a sentence or two each. The conclusion does not reveal the full findings but gives the gist and leaves reasons to read the full paper. An abstract allows readers to efficiently decide if a paper is relevant without reading the entire document.