Question about RSS Readers

Sorry for posting this question, but I'm really new to the RSS feeds and readers.

From what I understand, an RSS reader, (the one I use is SharpReader), basically is like an e-mail program like Outlook. The RSS reader downloads a small file that has a few sentences summarizing the whole entire article.


So my question is, does it download the whole article from the subscribed website or just the little file that summarizes the article, and from there there's a link for the real article online?

It usually depends on how you set it up.

I use Thunderbird to grab my RSS feeds, and there's an option where you choose how you want it to act.