Simply a booking/reservation that's been made, but no ticket has been issued.

I do this with my Oz tickets all the time. Using my regular consolidator, I make a booking. It's a confirmed reservation, with a PNR etc. I can pre-allocate seats. But no ticket (electronic or paper) has been issued - and, importantly, I haven't paid the TA anything other than a token deposit. I have full flexibility on the booking, changing dates, flights, routes, etc. as the ticket restrictions don't bite until the ticket has been issued. I can even cancel the whole thing and owe nobody anything except whatever the consol wants as a cancellation fee.

About 2 months before the outbound date, I have to cough up the ticket price and the e-ticket is then actually issued. (It's usually on a 60 AP - the ticket must be issued 60 days before the outbound travel date, or the reservation will be cancelled.) From this point, I have a ticket number - and a whole host of more stringent restrictions applies. Notably, from that point I can no longer change the outbound date without cancelling the entire trip.