The summary field is displayed as the shortened (teaser form) of your article. This will show up, for example, on a listing page of articles. It should capture the essence of your article and ideally be two to three sentences.
The Drutopia distribution is built in a modular way, so that you can turn on and use only the particular “features” or pieces of functionality that you want on your site. Learn about the content type features you can choose from.