A blog is a personal online journal (web log).

A post is a single blog entry.

A blog site is the location of a blog online, indicated by its URL.

A blogsite is a website combing feeds from multiple sources.

You can find a more detailed list here.

If you lose a WordPress blog post, there are two retrieval methods I found on the Web.

Use Google search
 In Google search, type “site:” followed by your blog site’s name.
site:canproofread.com/WordPress

Use Google Reader (link to source of information)

1. Sign up for Google and Subscribe to your RSS Feed in Google Reader.
2. Press CTRL + A to select the blog post in Google Reader.
3. Right click and select “View Source” to pull up the HTML Code.
4. Press CTRL + C to copy the HTML code.
5. Log into your blogging dashboard and Save the HTML code as a draft post.
6. If using WordPress, Go to Tools in the WordPress dashboard then Export.
7. Select All Authors, then hit Export.

Here is an excellent blog on backing up WordPress.