The Snap! system includes the Description Meta Tag.
The description appears as a text area where you can enter a few sentences representing the resume of your page. This is used in 2 different places:
1) In search engines when a result is shown about that one page, the search engine may decide to show your description instead of the content of the page itself;
2) When your page is pinged and the received decides to show your page, it may either pick the page teaser or the description.
When writing with SEO in mind, you want to remember that the description should not include the question and answer of your post. If you give away the answer, why would I click on the link to get to the full article?
To access the description of a page click on the "Meta tag" field set while editing the page then enter the description in the field of that name.