Every lot in the City has a zoning designation. Zoning describes what a property owner can do without getting explicit permission on a particular property. An owner that wants to do something that the zoning does not allow will have to seek a varience and will usually need to go through the Uniform Land Use Review Process.
You can find out the zoning for a particular property on NYCommons.org (like this one) by clicking on the OASIS link on that property's page. OASIS will open in a new tab with a "Location Report" section on the right hand side of the screen. In the Location Report, look under "Property Characteristics."