The Spanish language developed (from mostly Latin origins) in the Iberian Peninsula and ultimately came to mean the language spoken in Spain. Typical features of Spanish phonology include lenition (Latin vita, Spanish vida) and palatalization (Latin annum, Spanish año); both can however be found in most Romance languages.
Actually, there are regional variations among the various regions of Spain and Spanish America. Castellano, the variation spoken in Castilla, the region around the capital, Madrid, is commonly taken as an international standard. Catalan is a distinct language spoken in Catalonia, the region around Barcelona. Other languages used in Spain include Galego, which is spoken in Galicia, and Basque.
In the Americas, the first Spaniards to settle brought some of their regionalisms with them. Today you can find distinct accents in different nations of Spanish speaking America. Typical of the Americas is the pronunciation of <ll> as /j/ instead of /l_j/. In Spain, too, <ll> is now pronounced as /j/ rather than /l_j/. This phenomenon is called yeismo. In Argentina, /j/ is generally pronounced as /Z/ as in French 'jour'. This phenomenon is called z<caron>eismo. Also typical of Latin America is seseo. The European Castilian phoneme /T/ (as in ciento, caza) does not exist in American Castilian, it fell together with /s/ (as in ser, casa).
Regulated by the RAE (Real Academia Española).
Phonemes of European Spanish
/k, g/ /g/ has two allophones in European Spanish, namely [G] and [g]. [g] appears only at the beginnings of words (word-initially).
/f, T, s, x/
In South American Spanish, there is no /T/. /x/ has allophones [h], [ç], [x] in South America.
/tS/ (is pronounced as a plosive in European Spanish, something like [t_j]. In South American Spanish, on the other hand, there are mainly [tS] or [S] pronunciations - like French /S/ that has also developed from /tS/.)
/m, n, n_j/
/l, l_j/ /l_j/ is now almost extinct; it certainly is in American Spanish, creating a new /j/ phoneme: <guerrilla> /ge'Rija/.
/r, R/ /R/ is a flap or tap. Minimal pair: pero /'pero/ - perro /'peRo/
/a/ - /e/ - /i/ - /o/ - /u/ ???
See Common phrases in different languages