A Series Type is a category within which series are kept. When creating a class a studio must select one or more series types that can be used to book the class.*
Some examples of this are 'Standard Series' and 'Lunch Time Special'.

A Series is a product within the series type that is bought to be used to reserve a spot in a class.
An example of this would be 'Standard Series - 10 Pack', 'Standard Series - 20 Pack', and 'Lunch Time Special - 5 Pack'. The 'Standard Series' packages are part of the 'Standard Series' series type and the 'Lunch Time Special' package is part of the 'Lunch Time Special' series type.

*Please note that if a series type is set to be free and applied to a class, that series type is the only series type that can be used for that specific class.