Regielya, there may be some confusion in the thread because there are two transactions typically involved in ordering travel on-line: 1) buying an airline ticket; and 2) getting a boarding pass to get on the flight.

If you buy a ticket, and it is an electronic ticket, sold by most airlines, it exists as soon as you pay for it. All you need for the airline to access the ticket is the confirmation number of the transaction, or ticket number as proof, if you have no printer access. Most should be able to give you a receipt for the ticket at their ticket counter, or send you a printed copy by mail.

Most airlines which sell you an electronic ticket will allow you to print a boarding pass from the airline's website sometime prior to check-in time, or at the airport; or the airline check-in counter will print one for you. A growing number of airlines allow electronic ticket holders to get a smartphone boarding pass which both the security inspectors and airline accept.