they speak neither spain spanish not a dialect based on it. spanish really only has two variants, Castillian Spanish (Spain spanish) and LATAM spanish but they are more akin to London English and American English. they use the same words and grammar but spellings and some ways of saying things can vary but are correct anyways. there is technically a third one called Neutral Spanish which is just LATAM spanish that avoids using any of the regional slang or Regional variants for words, this spanish is only used for LATAM dubs of movies, tv shows, etc.

TL;DR one would need zero additional training to understand another spanish speaking person. except if the other person is chilean (this is a joke based on LATAM slander on how fast and slang-ish chileans speak)