Spotlight on your Mac
Spotlight 
is an easy way to find anything on your MacBook Air, 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.
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.
Convert currencies and measurements. Enter a currency—like $, €, or ¥—and an amount, then press Return to get a list of converted values. Or specify a unit of measure for measurement conversions.
Open an app. Enter the app name in Spotlight, then press Return.
Turn off Spotlight Suggestions. If you want Spotlight to search only for items on your MacBook Air, open System Preferences, click Spotlight, then click to deselect Siri Suggestions. You can also make other changes to the list of categories Spotlight searches.
Learn more. See Use Spotlight on your Mac in the macOS User Guide.