How is train PNR generated?

Related questions

1. Can we travel in train with PNR number only?
2. Will WL 4 get confirmed?
3. What decides train number?
4. What is the vikalp option in Irctc?
5. Is RAC confirmed ticket?
6. What is PNR number Qatar?
7. Is RAC is confirmed ticket?
8. Will WL 15 get confirmed?
9. Can WL ticket be confirmed?
10. Can we show SMS as train ticket?

Tags

1. #booked
2. #system
3. #classic
4. #stations
5. #upper
6. #passenger
7. #railway
8. #record
9. #number
10. #corner
11. #automatically
12. #ticket
13. #stands
14. #tickets
15. #digit
16. #after
17. #found
18. #generated