What is a Sul Ponticello?
: with the bow kept near the bridge so as to bring out the higher harmonics and thereby produce a nasal tone —used as a direction in music for a stringed instrument.
What is the difference between Sul Ponticello and sul tasto?
Sul ponticello ("on the bridge") refers to bowing closer to the bridge, while sul tasto ("on the fingerboard") calls for bowing nearer the end of the fingerboard.