A page abstract is a summary of, or introduction to, the content of a page. It is used by internal teaser components that target that page. The target page title, abstract and default image are automatically rendered in the teaser component. These elements can be overridden by the editor when the teaser component is created.
All Magnolia templates feature an Abstract field on the target page. This field resides in the header dialog on all pages except the home page where it is in the Page Info dialog.
The abstract should be included when the page is created to make teaser creation easier. The screenshot below shows a selection of teasers linking to the same target page in the default rendering. The components are the Horizontal Tabbed teaser in the main area and single internal teasers in the extras and promos areas