You can enjoy a train journey only if you have a reservation in the train. Without a reservation, traveling in trains is tiring and difficult. When you reserve a ticket in the train, you get a seat to travel, and a berth to sleep at night if it is a long-distance journey, including the overnight journey. There is a TTE in every coach to check if you are traveling with a ticket or not. If you are caught traveling without a ticket, you are punished according to the rules and regulations of the railway. Nowadays it is also necessary to carry a valid photo ID with you when you travel in the train.
There are only limited seats in trains and after they are booked, you will not get a reserved ticket when you book tickets. However, you can still book tickets in RAC or Waiting List. You will get a seat in RAC and you can travel in reserved coaches. Usually the side seats are provided for those in RAC. If enough cancellations are made you may get a berth too. If your ticket is in RAC or Waiting List, it important that you have to check the railway reservation status until you get a confirmed ticket.
If your ticket is in the Waiting List even after the final charts are prepared, you cannot travel in reserved coaches. So it is important that you check the railway reservation status to ensure whether you get a confirmed ticket and that you can travel in the train without any problem.