How Do Referrals Work

I'm just curious about how referrals work within the industry. How much do they matter, i.e. if a candidate has a referral from an analyst and a solid resume are they almost guaranteed to get a first round? How many referrals are analysts allowed to submit? Also, I got an email notification saying that I've been referred to one of the middle market banks, do all banks send you an email if you have been referred? Anyone who is in the industry that could shed some light on this that would be fantastic, thank you.