Google Foobar is a way for Google to recruit developers based on search history - roughly determing basic skill level & area(s) of competency.
Rather than sifting through a list of applicants (of undetermined skill) or trying to entice people through emails or recruiters, instead pique their interest with an invitation only challenge through Google.com.
Once you've gotten over the surprise of the immutable Google search changing you can start to play.
Source: IBTimes
Add all solutions to completed challenges (time is constraind at the moment)