Up to now, we've focused on actual content. You've seen how you can optimize articles to present their content in a clear and well-structured way. However, web pages also contain information that's not shown to site visitors, but is aimed specially at search engine robots: metadata.
Metadata is information about the contents of the HTML document hidden in the documents source code. Browsers (and search engines) will read it; humans won't know it's there (unless they specifically look for it by selecting the View Source option in their web browser).
By default, your Joomla!-powered site will only contain some dummy metadata, consisting of a short description and a few Joomla!-related content keywords. Let's change these to something more appropriate.