The value must be a free-form string that describes the page. The value must be appropriate for use in a directory of pages, e.g. in a search engine. There must not be more than one meta element with its name attribute set to the value description per document.
"property-name" — adds a property to a microdata item. The name of the property can be a word or URL, and the value is the ‘content’ of the element with this attribute.