SplinterGlossary: Regular Foil
Regular foil cards are much more numerous (and less expensive per BCX) than gold foil cards. Only a very small percentage of the Splinterlands cards turn out to be gold foil. See more details here.
Except for a 5% bonus that gold foil cards offer on winning battles, in combat, there is no difference between a regular foil and its gold foil version. For cards at the same level, their stats are identical in combat.
While in combat they are the same, in Brawls there are frays specially created for gold foil lineups. Equally, there are tournaments that require GF lineups.