I'm wondering how I can get my site to display preview information for specific search terms. I notice this occasionally from time to time and it would work really well in a question-answer based system I've built. You can see this live by Googling "Add a comment in word," and it's the content box that appears at the top of the search results.
Edit: I believe they're called Google answers. From what I've read, they're scraped from sites by Google for popular search results, but I'm hoping they can be implemented manually as well.
Unfortunately, you can't. This is called a "Knowledge Box" and is a new(ish) search feature that Google has implemented to assist in answer usability and is primarily show from to high-authority website's (brand's) such as Wikipedia, Microsoft..etc.
The answers do not actually being generated in real-time, but being pulled from a knowledge base that Google has pre-created called the "Knowledge Graph" which is also used in general search to help improve relevancy.