Spotlight on your Mac
Spotlight 
is an easy way to find anything on your iMac, such as documents, contacts, calendar events, and email messages. Spotlight Suggestions offer info from Wikipedia articles, web search results, news, sports, weather, stocks, movies, and other sources.
When you search with Spotlight, the preview area on the right provides search results you can interact with—make a call, send an email message, play a song, get directions, even convert currencies. Spotlight can provide answers to math questions or define words, all on your desktop.
Search for anything. Click at the top right of the screen, then start typing.
Tip: Type Command–Space bar to show or hide the Spotlight search field.
Get flight info. Enter the airline and flight number in Spotlight to see your flight status and a map, without having to open Safari.
Preview your results. Click a search result and view it in the preview on the right. Sometimes that’s all you need to do—click items or links directly in the preview. You can also double-click a result to open it.
Open an app. Type the app name in Spotlight, then press Return.
Turn off Spotlight Suggestions. If you want Spotlight to search only for items on your iMac, you can turn off Spotlight Suggestions in Spotlight preferences. Click the System Preferences icon 
in the Dock, click Spotlight, then click to deselect “Allow Spotlight Suggestions in Look up.” You can also make other changes to the list of categories Spotlight searches.
Learn more. See the Apple Support article Use Spotlight on your Mac.