Search with Spotlight
Use Spotlight to search for things like apps, documents, images and other files. In OS X Yosemite, Spotlight suggestions offer additional results like Wikipedia, news sites, Maps, iTunes, movie listings, and more.
To open Spotlight, click the magnifying glass icon in the upper-right corner of the menu bar, or press Command-Space from any app.
Spotlight appears front and center when you open it. To search for something, type words related to it like an app name, a word contained in a document, or a tag you've attached to a file. You can also search for items like a Wikipedia article, or the location of your nearest Apple Store.
As you type, Spotlight autocompletes the search field with suggestions. You don't have to finish typing to open a suggested item, just type the first few letters and press Return. It's a convenient way to quickly open your favorite apps.
Use your pointer, or the up and down keys on your keyboard to review the additional results in the Spotlight window. Spotlight shows you a rich preview of each result. This way you can make sure a result is what you're looking for, and see information you want without opening another app.
Double-click a highlighted item or press Return to open it. Documents and apps open directly from the Spotlight window.
Spotlight results also include dictionary definitions, currency conversions, and quick calculations. Type "100 dollars" or "2+2" in the search field to see the result.
You can opt out of Spotlight Suggestions and Bing results and continue to use Spotlight to search only your Mac. Go to System Preferences > Spotlight > Search Results and deselect Spotlight Suggestions and Bing Results. You can turn off other options from this preference pane as well. Go to System Preferences > Spotlight and click on "About Spotlight Suggestions & Privacy" for more details.
You can also opt out of using Location Services with Spotlight, in System Preferences > Security & Privacy. If you turn off Location Services for Spotlight Suggestions, your precise location will not be sent to Apple. To deliver relevant search suggestions, Apple may use the IP address of your internet connection to approximate your location by matching it to a geographic region.
Some Spotlight features (like Bing search) require an Internet connection and aren't available in some regions.
You can learn more about using Spotlight and other features included with OS X from the Help included with your Mac. Click the Finder icon in the Dock, then choose Help from the menu bar to search for topics like Spotlight.