The <title> element
A textual title describing the HTML document.
Usage
This is only allowed inside the <head> element, and only one <title> element is allowed there.
The content of the element must be plain text, so you aren't allowed for example to use phrasing elements to emphasize a piece of the title.
A good <title> element should give an unambiguous title or name for the document.
It is used by browsers to allow a user to see what is being shown in different windows or tabs, and for the default title of bookmarks, and as the heading for a page's listing in search results.
Often the title might be the same as the top-level heading, such as in an <h1> element in the actual content of the document, but not necessarily.
Sometimes the title will have to be longer and provide more information, since it can be used in places where there isn't any other contextual information available.
A heading in the content on the other hand will be shown as part of the document, with subheadings and other content nearby which will help the user understand what it means, so it might not have to carry all the same information as the title.
Full list of attributes
All the usual HTML global attributes are available