What are city codes used for?

Answer 1

An international telephone number typically consists of a country code, a city code, and a local number, although some countries do not use city codes. A city code is another term for a telephone area code, although area codes are often quoted including a domestic trunk prefix that is always omitted for the city code.

Using a city code allows for shorter local numbers, since the same local number can be reused in different city codes in the same country.