Data manager - Classification Fields purpose

Hi all,

I have a question regarding the Classification Fields from Data Manager. More precisely, what is the purpose of this classification and how can we use it in Studio?

Many thanks

Documentation:
Classification Fields

Data points which refer to a document as a whole. For instance, the Expense Type of a receipt (Food, Hotel, Airline, Transportation) or the Currency of an invoice (USD, EUR, JPY) would be examples of Classification fields.

When I loaded the default po schema in to data manager it had showed currency as classification field automatically…