If I search the word in Google is “twitter”.
Google displays the first result like the below.
Twitter
Twitter is without a doubt the best way to share and discover what is happening right now.
twitter.com/ - Cached - Similar
Search How To Contest Account Suspension
Blog An API
Twitter_logo_header Twitter Status
More results from twitter.com »
How can they display Search, blog, Twitter_logo_header, etc.?
These links are called Site Links, and point to highly rated pages on your domain.
Usually these links are created automatically if your site is strong enough for a specific keyword, and you can tweak it a little by blocking pages you don’t want to appear there from Google Webmaster Tools (http://google.com/webmasters) under ‘Site Configuration’, ‘Sitelinks’.
More information on this topic available at the following Google help page – http://www.google.com/support/webmasters/bin/answer.py?answer=47334&hl=en