Imagine you have a CMS site set up so it's using an application layout. Somewhere in that layout you have: <meta name="description" content="Something about the page">
Now, how do you dynamically populate content of that tag from the page? We can define {{cms:field:meta_description}}
tag.
In the admin area you'll be able to populate it and. Now you need to output that like this:
<meta name="description" content="<%= cms_block_content(:meta_description) %>">