What's the difference between Blogs and Articles?

Overview

In short, Blogs is the module of choice for bloggers and other authors of regularly updated content, while Articles can address a wider range of content management needs and typically require customization to meet those needs.

A Blog can be easily set up as a list of select Blog Posts, while Article lists typically display all Articles in the CMS (unless otherwise filtered by a developer in the site templates). This being the case, the Articles module is a bit more open-ended.

Here's an example of a use for Blog Posts:
http://layouts.ekklesia360.com/blog-layout-2/

Here's an example of a use for Articles:
http://layouts.ekklesia360.com/articles/

The two modules also have these differences:

Articles

More options for attaching media items (video, audio, image, document)
The concept of an article Series (a container of Articles, with the option of providing an image and description for the Series itself)
Multiple authors can be specified for one Article
RSS feeds for Articles can be created in the Feeds module

Blogs

A special URL for each Blog (www.site.com/your-blog-name/)
Each Blog can have its own link in the navigation
Commenting, with comment notification emails for the author
RSS feeds automatically created for each Blog