A key in determining whether an export license is needed from the Department of Commerce is finding out if the item you intend to export has a specific Export Control Classification Number (ECCN). ECCNs are five character alpha-numeric designations used on the Commerce Control List (CCL) to identify dual-use items for export control purposes. An ECCN categorizes items based on the nature of the product, i.e. type of commodity, software, or technology and its respective technical parameters.
An ECCN is different from a Schedule B number, which is used by the Bureau of Census to collect trade statistics. It is also different from the Harmonized Tariff System Nomenclature, which is used to determine import duties.
All ECCNs are listed in the Commerce Control List (CCL) (Supplement No. 1 to Part 774 of the EAR), which is divided into ten broad categories, and each category is further subdivided into five product groups. The first character of the ECCN identifies the broader category to which it belongs and the second character identifies the product group (see example and boxes below).
Commerce Control List Categories
0 = Nuclear materials, facilities and equipment (and miscellaneous items)
1 = Materials, Chemicals, Microorganisms and Toxins
2 = Materials Processing
3 = Electronics
4 = Computers
5 = Telecommunications and Information Security
6 = Sensors and Lasers
7 = Navigation and Avionics
8 = Marine
9 = Propulsion Systems, Space Vehicles, and Related Equipment
Five Product Groups
A. Systems, Equipment and Components
B. Test, Inspection and Production Equipment
Source : https://www.bis.doc.gov/index.php/licensing/commerce-control-list-classification/export-control-classification-number-eccn