Hi Hari,
You are right, there are actually 3 classifications for a product and these with their bried description goes as follows:-
ECCN:- It is an abbreviation for Export Control and Classification Number. This is the classification for a product for compliance prospective i.e for the determination of a particulat license to be used for that case.
HTS Codes(Import):-It is an abbreviation for Harmonised Tariff System codes. This is basically a 10 Digit code( can be less than 10 as well but always greater than 6 charaters) used for classification of the products when dealling with Imports. This is based on the HS system and derives its intial 6 characters from that while the rest of the 4 digits are country specific. Thjis is more specific to identify as product more accurately.
HTS Codes (Export) or Commodity Codes:- This is also basically a 10 Digit code( can be less than 10 as well but always greater than 6 charaters) used for classification of the products when dealling with Exports. This is also based on the HS system and derives its intial 6 characters from that while the rest of the Charaters are country specific. This is more statistical and less product specific in nature as compared HTS codes for Imports. An Example for this is Schedule B numbers used in US exports. In that, the first six digits will be from the HS codes like HTS codes for Imports but the last 4 digits are always Zeros unlike HTS codes for Imports.
I hope you got it now.