Different from means not the same.
e.g. Sara's taste is different from mine.
Different than: In US English, than is an alternative to from before a clause.
e.g. Sara's appearance was very different than I'd expected.
NOTE : On GMAT different than is always wrong when comparing two nouns.
Different than is only correct when a sentence compares a noun and a clause.
On GMAT sentence correction if you come across a question comparing two nouns and a choice with the phrase different than eliminate that choice.
Since the 18th century, language critics have singled out different than as incorrect.
