The example that has been used in both The Wall Street Journal's report of the changes and Mashable's interview with Singhal is that of a lake - if you type in a specific lake, Google will in future not only send you to websites devoted to said lake based on keywords, but will also deliver attributes of the lake, such as location, altitude, depth etc.
Currently as you can see in the image above, results in this instance are getting a little closer to what semantic search results could be like, with a Google Maps result showing location, but they also include the Wikipedia entry for Lake Michigan, images, and a live web cam.
The type of search that will come in future seems more akin to an advanced encyclopedia, and is interesting in that search will yield smarter, somewhat more human results, treating a search term like a question, and attempting to deliver an answer you would expect from someone knowledgeable on the subject.
It's worth noting that an article by Danny Sullivan on Search Engine Land today argues that this is just PR on Google's part, as he argues that Google already does this kind of search, _µ__so the changes aren't all that big. At any rate, it's not yet fully clear what impact the changes, whether gradual or sudden, will have on other aspects of Google such as advertisements, and when the changes will be fully implemented, but it's interesting to see what direction that company is sending their engine in, and how we're going to be using Google Search in the future.