How do I download apps from the App Store such as google or Facebook on a MacBook Air?

Large websites such as those are usually accessed through a browser on computers; the standalone applications are for mobile devices.

(178332)

There is no Facebook App for Mac, you can access it through its website directly and most larger websites like those don't have Apps for Mac or even Windows.

Google is a company, they make tons of things, some may have apps, some may not, what exactly are you looking for from Google?