How does referral concept work?

Hi,

I came across a job portal www.yellojobs.com where they say if I refer a friend for a job and he/she gets selected, I will get cash rewards. I want to know if it is true or a fraud kind. They say they have more than 60 crores cash rewards to be given. I am kinda excited.
If anyone has come across this concept, please advice me how it really works.