The document defines an abstract as a short summary of a longer work that provides readers with a quick overview of the paper's content and organization. An abstract usually consists of one paragraph containing 6-7 sentences and 150-250 words. The document discusses two main types of abstracts - descriptive and informative. A descriptive abstract only describes the major points of a work, while an informative abstract summarizes the paper's background, purpose, methods, results, findings, and conclusions. The document provides guidance on writing an abstract, including using active voice, past tense, and avoiding unnecessary details.