Use age groups when you need to charge different amounts for adults and children. Add as many or few age groups as you need. Leaving either the Start or End blank will make them unbounded in that direction.
Example Age Groups
Adults 13 and up, Children 3 - 12
Adults 13 - 65, Children 3 and younger
You cannot have overlapping ages
This will not work
Adults 13 and up, Children 3 - 13