If you want to any where by train without reservation then you have to go in general coach of train. You can book online ticket for general coach of any train.
After book online ticket for general coach you are not authorized for take seat in reserved coach. The reserved coach of trains are –
(1) AC sleeper First class
(2) AC Sleeper 2 Tier (Second AC)
(3) AC Sleeper 3 Tier (Third AC)
(4) Third AC Economy
(5) AC Chair Car
(6) Non AC Sleeper First Class
(7) Non AC Sleeper 3 Tier
There is an another class in every train which is called “Second Seating” which is equivalent to General Coach. You can seat in any coach in that train (except- reserved coach). The price of online ticket for general coach is similar to general ticket, but you have to pay Rs. 15.00 in additional for each tickets.
The main problem in online booking of general ticket is that this ticket is valid for only that specific train for which you have booked it. Where if you purchased a general ticket for passenger train from ticket counter of railway station then you are free to go by any passenger train. If you have purchased a general ticket for express train from ticket counter of railway station then you are free to go by any passenger train or express train.
So, be sure for your train before book online general ticket for any train.