Summary property - where is it on a page?

In Find > Configure, what does the Summary property read on a page in Epi? Is it the Page description field on the SEO tab? 

In the Epi Find User Guide, it just describes the Summary property as "The introduction, summary, abstract, or similar property type." Is that the first paragraph of content on a page?

I'm using Epi as a content editor, not a developer, so the simpler the response, the better for me :)