It's considered good SEO practice to not only add a specific page heading (contained in the H1 element), but to also make sure that each page has a descriptive HTML page title (the title element). Page titles are one of the most important ranking factors for search engines, so it's important to make sure they contain relevant information about the content.
The contents of the title element aren't displayed on the web page itself, but they're shown in the browser title bar. The screenshot below shows how the page title Using Joomla! is displayed in Mozilla Firefox:
In most browsers, the page title is also displayed in the current browser tab, as shown in the screenshot below (taken from Google Chrome):
