Title Tags and Attributes
Title Tags are located in the <head> section and have 4 purposes:1. Let search engine spiders and humans alike know what the page is about.
2. Provide a title for browser tabs.
3. Provide a title for when the site is added to "Favorites".
4. Displays in the search engine results as the link to the site you’re (potentially) looking for.
Title Attributes are located within the <body> and have 3 purposes:
1. Provide additional information about an element on a page.
2. The content of the title attribute will usually show up as a "tooltip" when hovering your mouse over it.
3. Title Attributes are spoken by Screen Reading Software (JAWS, Orca, BrlTTY) when no explicit label is set in form elements (they are also a level 2 requirement for WCAG compliance).
The attribute was used solely within links in the previous releases of HTML and pages would not validate if it was included anywhere else in your code, with the release of HTML5, the title attribute can now be used most anywhere and not affect validation.
Final Thoughts:
The title tag as well as the attribute are supported by all major browsers, give humans and spiders a description of what to expect, and should be used in all of your SEO/SEM endeavors.