The concept of the city-region can be understood as a functionally inter-related geographical area comprising a central, or Core City, as part of a network of urban centres and rural hinterlands. A little bit like the hub (city) and the spokes (surrounding urban/rural areas) on a bi-cycle wheel.

The area around a city which serves and is served by the city (not just the administrative area of a city/conurbation but also the urban and rural fringes/hinterland hence usually far larger). (source [..]