An abstract is a brief summary, whether of a proposal or a finished study. Abstracts play an important role in the research literature, and they are required in proposals (usually), dissertations and in research articles in most refereed journals. Abstracts and titles are at the heart of the hierarchical indexing system for the research literature, which becomes more and more important as the volume of research continues to build. This indexing system enables researchers first to scan a title, to see if they need to go further into a project. If so, they can go to the abstract, which will tell them more, and perhaps enough.
[Punch, K.F. (1998) Introduction to Social Research. Sage Publications (UK)]