Google Search app for Windows 8 devices can directly search Google from the Windows 8  Start screen instead of going to desktop and then doing the same from browser.
This app is available in Windows store, simply search for it. 🙂
Once installed, it will be available on the Start screen.
Search for stuff as usual but this time the results will appear within this search app.
Besides that, there are various other settings like managing search history, opening the search results in a browser, accessing other Google apps (like Gmail, YouTube and so on).
Also, this app integrates with Windows 8 search charm. So, when accessing search charm (Windows key + F), an additional option of searching using Google Search will now be available. (To get a list of common keyboard shortcuts for Windows 8, please refer to this earlier article).
Happy searching.