Yes, actually, you're right! A hub's summary gets fed into the "description" metatag of that webpage.
Metatags are various shorthand bits of information describing webpages for computers and search engines, like the information about a book in a library card catalog.
You can see metatags of various kinds by choosing "View Source" from your web browser and then searching for the META tag. (Just search for "META").
Nowadays, metatags are ignored by search engines as far as using them to help the search engine decide how to rank the page, because too many people stuffed their metatags with fake keywords or descriptions that didn't really match the content.
However, the "description" metatag -- our hub summary -- is still important, because it's often displayed as the excerpt, the quote, when our hub appears in search results. Google may pluck a quote from elsewhere on the page that matches the searcher's query, but sometimes it uses the description. Bing and other search engines are more apt to display that description.
So it's important to write it for human readers. It's like your job interview, a quick first impression to show that your page is competent, clear, well-written, and (most of all) that it covers the topic a searcher is looking for. So tell what your page is about -- be specific! -- and use engaging, appealing language.
When I'm trying to leverage every visitor I can, I'll often phrase the description as a question, because people tend to click on questions to find the answer. :)