When a user searches for a brand (i.e., Coke), the company that owns the brand can buy the results page and customize the look and design of the page. It could show commercials, fan sites, et cetera. Actual search results would still appear as normal, but the look of the page could be completely branded by Coke. This would be a much more interactive, robust experience compared with the standard sponsored text ad on the right.
Imagine launching a new product that receives huge buzz across the web on Day 1. This buzz would lead to massive searches on Google. Rather than a little text ad, you "own" the page with press release information, a video overview, a live chat using Google Chat, widgets, et cetera. Now this is the way to launch a product!