The title tag is an HTML element found in the found in the head tag of a page. As its name suggests, this tag includes the title or very brief summary of the content users can expect to find on the page.
A typical title tag:
<title>Your Source For Blue Widgets & Green Widgets | Acme Inc.</title>
The title is used in many places, but perhaps the two main areas of importance are the browser's title bar and the anchor text of your page's snippet on the SERP. Search engines give content in this area perhaps the highest weight of any content area on the page, so it's important that this area is optimized well.
Other Guidelines for Writing Effective Titles
Rewrite the title for each URL using your most important targeted keywords and keeping it under 570 pixels wide. Here are some other best practices for writing good titles:
Each title should be unique. Ideally, no two URLs should share the same title.
Place your most important keywords as early in the title as possible
Keep title length to 570 pixels wide, which is about 50-60 English characters
Keep your brand name or site name towards the end of the title
Titles should be natural and human readable, not just comma-separated keyword lists
For large sites, consider writing rules to programmatically generate your page titles, but make sure these are human readable and make sense