The Search in Windows 8 has been significantly improved when compared to all previous versions of Windows. To search for a file or run a program in Windows 8 from the Start screen just start typing what you're trying to find or want to run.
As you begin typing, the results will start appearing on the left-hand side. In addition to being able to search for files and run programs, the Search also supports limiting the search to apps such as Finance, People, Maps, Photos, Mail, Music, Videos, Weather, and much more. If what you are searching for is not a file or program, click on the app you wish to use as the search.
For example, if you were searching for "New York" and selected the Weather App you would be shown the weather in New York, NY.
By default, Search organizes the available Apps by how frequently they are used and then in alphabetical order. If you want to keep your favorite app at the top of the Search list, right-click the app and choose Pin. Pinning the app will lock it in place regardless of how often it is used. If there is an app you don't want (e.g. Finance) you can turn on and off any of the search apps through the PC settings, which is found under the Settings in the Charms.
Bonus tip: The Search is also found through Charms and can also be opened by pressing Windows key + F.