Fresher Guy, Curious about Companies Referral System Functioning

Currently I'm actively looking for full-time opportunities out there, and requesting employees for refferals through linkedIn DM. Since It's my first time exploring job opportunities off-campus I was just curious to know about the refferal system. I had few doubts: 1. If some employee of the company refers me at their end for a particular job, then is it also necessary that I apply for that same job from company's career portal and mention referring employee name/email on the application (if asked). 2. What kind of details does a referring employee gives so that the candidate can be uniquely recognized as an referred applicant, is it resume or just the name?