In cognition, abstraction is a higher order type of thinking in which common features are identified (or abstracted). This cognitive process of isolating common characteristics between different things is essential for many high level forms of thinking such as learning from experience, inference, and forming judgments. When something is abstracted it becomes an abstraction or an abstract idea. Abstract concepts differ from concrete or literal concepts.
For example, the general concept of love could be said to be an abstract idea. It is somewhat ambiguous and though it shares common characteristics is is not a concrete, absolute concept. Another abstract concept would be war. War can take on many different forms and ideas. A concrete concept would be World War I. This is a specific, concrete event. Algebra uses abstraction in that letters are used to represent unknown numbers.
Abstraction, in the case of professional literature, is the process of condensing information from an article or monograph about research into the most salient points so that the prospective reader will understand the subject of the paper and the general conclusion that was reached. Referred to as an "abstract", this paragraph serves as a preface to the article or paper itself.