How Does Referrals at Goldman Sachs Work??

My cousin brother graduated from a T1 clg CSE and got placed in Goldman Sachs recently , i am about to start my college , My brother told my parents that i should just focus on skills and studies in college and after 4yrs he will get me placed at the company via referrals

But the thing is i have a bit low board %age and idk how referrals work? like can someone explain it in brief ?