An urban agglomeration is the urbanized region that extends without interruption across several administrative districts; It normally includes a central city and satellite towns or cities that it has absorbed in its growth. Agglomerates tend to be formed around large administrative centers.

The name urban region refers to the urban agglomeration in which several cities perform functions of a similar order, or perform different functions but of similar rank.

In an agglomeration, the two large parts that make up its urban structure can be clearly differentiated:

The city's tertiary activities (commercial, financial, administrative and cultural) and the largest source of employment. It has an organized character and has most of the infrastructure services and urban equipment. From here the different transport routes that connect it with the suburbs generally start radially.