A “Tax and Duty” calculator provides the total landed cost to the buyer (from your eCommerce platform). It clearly provides the shipping fee, taxes and duties for a specific sales order. In general, duties and taxes are determined based on the product type, its value, country of origin and the final country of destination.
Depending on the country, other terms could be used to refer to “tax”. For example, in the EU “tax” is referred to as VAT – Value Added Tax.