What is Accessory Use?
Accessory Use meaning An accessory use is a use that is incidental to and customarily found in connection with the principal use. An accessory use must be conducted on the same zoning lot as the principal use to which it is related, unless the district regulations permit another location for the accessory use. (Off-site accessory parking facilities, for example, are permitted in certain zoning districts.)
reference: Glossary of Planning Terms – NYC Planning