The content of the title
element should identify documents
[…] even when they are used out of context, for example in a user's history or bookmarks, or in search results.
So for a typical website, each page’s title
should consist of two parts (in that order):
- what the page is about ("About Us")
- to which site this page belongs ("Example Dog Grooming Company")
(Exception: the home page, which can contain the site name only.)
The first part often contains more than just the main content heading, e.g., metadata like category or page type ("… - Blog", "Review: …", etc.).
For the second part it can make sense to abbreviate the site name if the shorter form is also meaningful for and known by your visitors.