Classical music & other terms

orchestra (giàn nhạc giao hưởng) is a large instrumental ensemble typical of classical music, which combines instruments from different families.
Choir (Hợp xướng) is a musical ensemble of singers.
Conducting them is different.

In music, a bow (cây vĩ) is a tensioned stick which has hair (usually horse-tail hair) coated in rosin (to facilitate friction) affixed to it. It is moved across some part (generally some type of strings) of a musical instrument to cause vibration, which the instrument emits as sound.
bow of a ship; bow to shoot arrow

A fiddle (vĩ cầm) is a bowed string musical instrument, most often a violin. It is a colloquial term for the violin, used by players in all genres, including classical music.