Page title is the title of a page, which comes from the <title> in your HTML code. For example, if your website has the following code, the value of the 'Page title' dimension would be 'MyWebsite'.
<!DOCTYPE html>
<html lang="en">
<head>
<title>MyWebsite</title>
</head>
<body>
<p>Hello, World!</p>
</body>
</html>