Do I need to buy a ticket for children and what are the special prices with ÖBB?

These are the conditions when you travel with children on ÖBB trains:
Children from 0 to 5 years old inclusive: they travel for free when accompanied by an adult but they must be included in the reservation at the time of booking and will be given a free travel ticket. Please keep in mind that children riding free on Austrian trains, particularly on night trains, will not have their own bed. If you want to reserve a bed, you must purchase a Child ticket.
Children from 6 to 14 years old inclusive: get a 50% discount on their ticket. The discount will automatically be applied when you enter their age.
Teenagers from 15 years old: the full price will be charged.