Что такое Primary и Display artist?

Display Artist: Please write artist as you would like to see on stores , (Example: ATB & Tiesto ).

Primary Artists: - Please write all artist separately, Example:

Primary 1: ATB

Primary 2: Tiesto

Display Artist: ATB & Tiesto

Primary 1: ATB

Primary 2: (leave empty)

Display Artist: ATB feat. Heather Nova

Contributors - Featuring: Heather Nova 

Don't put in Primary with & or feat.:

Primary 1: ATB & Tiesto - INCORRECT

Primary 1: ATB feat. Heather Nova - INCORRECT