about

Description
about is a CreativeWork property designed to encode the subject matter of the content.

Because the range of about is Thing actually we can expect any Schema.org type instance as its value.

The typical usage is with the help of itemprop attribute inside of any HTML element. about must always be part of a specified CreativeWorks context (such as Article, or BlogPosting)'' by means of the first parent element defining itemscope attribute.

Examples
A simple example when description is part of a context:

The above example shows using about to encode that the current markup is an Article which is about a Place named Roots Restaurant.

One open question (we invite you to discuss) is in fact a general one. Can we reference a Thing by means of an URL?

E.g., is possible to annotate as: