Alfred is a search utility like Apple’s Spotlight, except with more features and flexibility. Among its myriad of useful tools is the ability to kick any search query out to the engine of your choice.
And choice you have. You can call on any built-in or customized search engines at any time. But Alfred also presents a list of go-to engines, called fallback searches, when it runs out of local results of your preference. Alfred’s defaults are Google, Wikipedia, and I believe one other, but you can see below how I’ve customized my options under Preferences > Features > Defaults Results.