HSN stands for Harmonized System of Nomenclature. 

The Harmonized Commodity Description and Coding System, also known as the Harmonized System (HS) of tariff nomenclature is an internationally standardized system of names and numbers to classify traded products. It came into effect in 1988 and has since been developed and maintained by the World Customs Organization (WCO) (formerly the Customs Co-operation Council), an independent intergovernmental organization based in Brussels, Belgium, with over 200 member countries.

The HS is organized into 21 sections, which are subdivided into 96 chapters. The 96 HS chapters are further subdivided into approximately 5,000 headings and subheadings.