How does backup of controlfile take place automatically (non-rman)

Below questions are refered to when RMAN is not used at-all, and I have not given any manual/explicit command to store backup of controlfile. 

Could you please explain me about 'SQL> recover database using backup controlfile;'. 

What I am trying to understand here is, if its possible to run this command even if a explicit backup of controlfile is not taken. 

I tried this and it works. 

so the question is where and when exactly is the backup stored ?

There is a obvious something trivial that I am missing out here.