I've done a few exercises in the site. While recruitment seems most likely, I haven't seen anything that explicitly mentions applying to work at Google or anything like that. There are coding challenges and a gamified leveling system based on how many coding challenges you complete within the time limit, but no mention of applications.
If I remember, I was blanking on the exact Python lambda syntax, so I Google'd "python lambda". I bet it had something to do with other searches I'd done in that session as well though, and I don't remember what they are.
<- Author of that thread.
The site is an interactive shell with progressively harder (but fun) coding challenges to complete. It's made to look like a *nix shell and has the basic commands built-in.