In June 2011, three main search engines (Google, Bing and Yahoo) created a new standard for semantic search: schema.org. They created a dictionary in order to turn into machine readable some information that only a human being could understand.
For example, the word "Avatar" could be a lot of things: it could be a film title, an user image on a forum and so on. We can understand what we're talking about using the context, a machine can't, it needs more information.
To help developers in this task, we have created an extension that allows them to quickly navigate inside the dictionary and pick the tags they need.