You can create either a Post or a Page. With a Post, the permalink is “?p=<post id>” and then you enable pretty permalinks to get something like “/name-of-the-post”, this is the Post-Slug. You can change this particular piece to be anything you want, because the underlying post number is fixed.
Now the second way of putting stuff on your blog is through Pages. These are essentially timeless, in that they are not fixed to a particular timebase and can be called seperate using the URL you’ve mentioned above.
So if you want to make a page just about hurricane Rita, you would go to Write->Pages and then write your content using the page-slug to be what you want. Usually the page-title will become the slug, but if you want the page to be called <domain.com>/hurricane-rita and the page title to be “My Views on Hurricane Rita”, then you use the page-slug..
Using the user-friendly names for both post and page slugs require that you have the Permalink feature turned on in WordPress. Once that happens, you can definitely access posts and pages by their friendly names as opposed to ?p=<id > and ?page_id=<id>..