Google Hot Trends is a feature of Google Trends which is designed to show the "hottest" searches in the last hour.
These aren't the highest volume searches; these are the searches with the greatest growth in search volume over a very short period of time.
These keywords are not stable enough to build a web site around, but they can make excellent blog posts. Blog posts can be crawled and indexed very quickly, so a blog post made early in the "trend cycle" can be a great source for inbound links.
The Hot Trend detail page will show you a list of related search terms that you might optimize for. It will also show you when the peak of traffic for this trend occurred, so that you can see how far behind the curve you are. In addition, it will show you snippets from news articles which may help to explain why this keyword is a "hot trend".
Hot Trends is also available as an iGoogle Gadget and an Atom Feed.