You've registered your interest, nearer the time the Telegraph (new sponsors) will contact you and offer you a variety of ticket options, you can then update your Registration to an e-ticket.
This allows you to enter competitions held by exhibitors or advertisers and also allows them to say to prospective exhibitors "We've got Xxx pre-registered attendees for each day".
Common practice in sponsored exhibitions now, exhibitors each get an amount of free & discounted ticket codes to give away.
Rob