Stories are a great method of posting content, or "blurbs," that you want to appear on the site. A story can be short or long, and can include all the cool stuff (images, links, file attachments, etc) of any other sort of content.
When you're going to post an announcement of some sort, the three basic methods are event (if you have a specific date and want it included in the calendar), blog post (if you'd like the content included in your personal blog), and story. Story makes the most sense for standard site posts that aren't date-related.
