Google added a new algorithms that generate alternative Page titles to make it easier for users to recognize relevant pages. "We use many signals to decide which title to show to users, primarily the <title> tag if the webmaster specified one. But for some pages, a single title might not be the best one to show for all queries, so we added the algorithm," informs Google Webmaster.
Adding, "Our testing has shown that these alternative titles are generally more relevant to the query and can substantially improve the clickthrough rate to the result, helping both our searchers and webmasters. About half of the time, this is the reason we show an alternative title," Google said.
"Other times, alternative titles are displayed for pages that have no title or a non-descriptive title specified by the webmaster in the HTML. For example, a title using simply the word "Home" is not really indicative of what the page is about. Another common issue we see is when a webmaster uses the same title on almost all of a website's pages, sometimes exactly duplicating it and sometimes using only minor variations," explains Google.
Lastly, we also "try to replace unnecessarily long or hard-to-read titles with more concise and descriptive alternatives."
Google notes, that they also, notify webmasters as and when they discover "titles that can be improved on their websites through the HTML Suggestions feature in Webmaster Tools."
This feature is available in the Diagnostics section of the menu on the left hand side.
For more information about how you can write better titles and meta descriptions, and to learn more about the signals that generate alternative titles, you can refer to this Help Center article.