Classic Wiki Zither

Any stringed instrument in which the strings run across a body or resonator, and that has no protruding arms or neck. By this definition, the zither family includes psalteries and hammered dulcimers, but the instruments most characteristically referred to as zithers are the fretted zithers of Europe. In south Germany and Austria, two highly developed varieties exist: the Salzburg zither, flat along its fretted side and curved out on the opposite side; and the less common Mittenwald zither, curved out on both sides. Both have a shallow, flat sound box with a round sound hole and, usually, five metal melody strings stretched along a fretted fingerboard.

Source encarta

Any stringed musical instrument whose strings are the same length as its soundboard. The European zither consists of a flat, shallow sound box across which some 30 or 40 gut or metal strings are stretched. The strings nearest the player run above a fretted fingerboard against which they are stopped by the left hand to provide melody notes; they are plucked by a plectrum worn on the right thumb. At the same time, the right-hand fingers pluck an accompaniment on the farther strings, which remain unstopped. The zither is placed across the player’s knees or on a table.

Source britannica