Roaming is the ability for a customer of mobile communications to automatically make and receive telephone calls, send and receive data, or access other services while travelling outside the geographical coverage area of the home network, by means of using a network of another operator.
Roaming can be either national roaming or international roaming. National roaming means that mobile subscribers make use of another network in geographical areas where there own operator does not have coverage. This is e.g. used by operators who do not have complete coverage in a country. International roaming is used when mobile subscribers travel abroad and make use of the network of an operator in the foreign country.