An abstract is a precise outline of a scientific work in order to give the reader an overview of the statements of the publication at the beginning.
General characteristics of an abstract are: * it should abstain from any evaluation * it should be as short as possible * it should have a clear, comprehensible language and structure * it should contain all essential facts explicitly and it should reflect exactly the contents and opinion of the original work.
https://de.wikipedia.org/wiki/Abstract (Wikipedia CC-by-sa-3.0)