Rule of Thumb: when you need to clasify a thing, use Type if it can be of only one Type, and Category if can have more than one.
Explanation:
In
Data Model Patterns David Hay makes a point discussing between the difference of a Type or a Category of a thing.
Basically Type is a N to 1 relationship (a thing can be of only one Type) and Category is a M to N relationship (a thing can have many categories at the same time).