An executive summary (it’s also known as management summary) is a short document describing an extensive report so that readers can get its main idea quickly. It usually contains background information, a brief statement of the issue, analysis, and conclusions. An executive summary is used as an aid to decision-making by managers, and it’s used as a part of the business plan.
The difference between an executive summary and abstract is the following: an abstract is usually shorter and consists of an overview, but an executive summary is a part of a document.