Domain parking is a business with a long history in the web. Basically, if you have a domain name without any content, you can use it to make a few bucks using domain parking services.
The basic idea behind domain parking is that, depending on the domain name you have, many users will access the domain from time to time. For example, a domain such as pizza.com will generate visits even if it had no content. People just type a name like this in the browser window and it will eventually arrive at their web site.
Domain owner can profit from this by adding links that users will eventually click, generating advertisement revenue.
Until now, Google had a domain parking service that was restricted to domains with large number of visitors. Imagine if Microsoft.com goes out of business: they could just park the domain at Google and share the ad revenue.
Now, Google is allowing this to all domain owners. It may become a great business for people that buy domain names, since they need no content. Just the name will be enough to generate some money.
The bad news, however, is that you can certainly expect a large number of new domain to be created just for this purpose. Which will make even harder to find useful things, unless you use Google... well, may that is what they really want, after all.