Historically, the provinces served mainly as transmission belts for policies enacted in Madrid, as Spain was a highly centralised state for most of its modern history.

The importance of the provinces has declined since the adoption of the system of autonomous communities in the period of the Spanish transition to democracy.

In addition, organisations outside Spain use provinces for statistical analysis and policy making and in comparison with other countries including NUTS, OECD, FIPS, CIA World Factbook, ISO 3166-2 and the UN's Second Administrative Level Boundaries data set project (SALB).

Most of the provinces are named after their capital town —with the exceptions of Álava, Asturias, Biscay, Cantabria, Gipuzkoa, the Balearic Islands, La Rioja, and Navarre, and a name reduction in Las Palmas and Castellón— and biggest town[7] —with the exception of Pontevedra (Vigo), Asturias (Gijón) and Cádiz (Jerez).

Seven of the autonomous communities comprise no more than one province each: Asturias, the Balearic Islands, Cantabria, La Rioja, Madrid, Murcia, and Navarre.