The owner is a term that describes subordination relationships between database objects.
For example, a configuration includes catalogs named Cities and Streets. Each city has its own list of streets. New York city (an element of the Cities catalog) is the owner of streets Broadway and 1st Avenue (elements of the Streets catalog). Washington DC city is the owner of streets Western Avenue, Eastern Avenue, and Southern Avenue.
Sometimes this term is used for describing the data structures where owners are stored. For example, "The Cities catalog is the owner of the Streets catalog". But this usage is not accurate and is considered developer slang.