In Part 3 of this series, Jarek Wilkiewicz details activating the small Knowledge Graph (built on Cayley) with Schema.org Actions. He begins by explaining how Actions can be thought of as a combination of "Entities" (things) and "Affordances" (uses). As he defines it, "An affordance is a quality of an object, or an environment, which allows an individual to perform an action."
For example, an action, might be using the "ok Google" voice command on a mobile device. The even more specific example that Wilkiewicz gives in the video (spoiler alert) is that of using the schema.org concept of potentialAction to trigger the playing of a specific artist's music in a small music store's mobile app.
To learn more, and to meet Jarek Wilkiewicz and his Google colleague, Shawn Simister, in person, register for the Semantic Technology & Business Conference where they will present "When 2 Billion Freebase Facts is Not Enough."