Title Tag
A title tag is the HTML element that states a page's title. The title appears as the clickable headline in the search results, in the browser tab, and as the default text when someone shares the page. It is one of the most direct signals a site can give search engines about what a page covers, and a basic element in all SEO work.
The title's role in the results
A title does two jobs at once. It tells the search engine what the page is about, and it gives a person a reason to choose that result. Google therefore assigns considerable weight to the words in the title when judging relevance, and the page's most important keyword usually sits early in well-optimized titles. Google measures title length in pixels and truncates around 50 to 60 characters, so only the opening is reliably visible. Together with the meta description, the title works as the page's advertisement in the results, and the pair drives much of its click-through rate.
Google rewrites titles that do not hold
Google is free to replace a title in the results and pull text from the page's headings or from anchor texts pointing at it. Rewrites typically hit titles that are too long, too generic or mismatched with the query, while a precise title describing the actual content is rarely touched. The guide to page titles and meta descriptions covers how strong titles are written in practice.