A page with no title

The content and headings here are fine. There is just no title tag in the head.

What the title does

The title tag is how a page introduces itself to a search engine and to anyone scanning a list of results. It carries the main topic and it is the first thing people read. When it is missing, the search engine builds its own title from text on the page, and that is usually worse than one you would write yourself.

Why it goes missing

A missing title almost always comes from a template. A content type never got a title field, or a component only renders the title when a value is passed in, or a migration dropped the head tags. The page looks fine to a person, so the problem is easy to miss until you check the head.