The <section> tag:
The section tag defines sections in a document, such as chapters, headers, footers, or any other sections of the document.
The <article> tag:
The article tag specifies independent, self-contained content.
An article should make sense on its own and it should be possible to
distribute it independently from the rest of the site.Potential sources for the article element:
- Forum post
- Blog post
- News story
- Comment
Basically these tags are semantic elements and the only real difference between them are readability and design preference.
You can read more about them here if you wish:
- http://www.w3schools.com/html/html5_semantic_elements.asp
- http://www.w3schools.com/tags/tag_article.asp
- http://www.w3schools.com/tags/tag_section.asp