free、reduced、fullのチケットの違い

http://www.weekendafirenze.com/milano/ordering.htm
に説明が出ています。

REDUCED TICKETS:

Half price tickets (just European Community citizens):
between 18 and 25 years old
school teachers
Free tickets:
non European Community citizens under 6 years old
European Community citizens under 18 and over 65 years old