So far, 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 it is aimed specifically at search engine robots. This information is called metadata.
Metadata is information about the contents of the HTML document hidden in the document's 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). Search engines may present the content of the meta description tag in the search results page. Although meta keywords aren't of importance for many search engines anymore, it won't hurt to add meaningful metadata to your site.
In Joomla, you can enter metadata on the following four levels:
Site-wide, through the Global Configuration screen
For individual menu links
For individual categories
For...
