there is 2type of ticket
1. prs ticket
2. e-ticket
first -prs ticket u book from counter.
though u want to book a prs ticket through internet u can book it by...
more... selecting I-ticket at the time of booking through internet
I-ticket is a mode of prs ticket.its need to book before 2-3days of ur journey.
second- an e-ticket is always booked on the website of irctc or applications partner of irctc through internet by using irctc.com or app like ngpay and others .there is some different mode of this type of ticket like paper ticket SMS TICKET and e-mail ticket. u can show to tte ur print out,sms or email with id while u r traveling
irctc send a sms and email after completing ur booking process on ur registered mobile no. and on registerd email id