Classic Wiki Mandolin

A mandolin is a musical instrument in the lute family (plucked, or strummed). It is descended from the mandore, a soprano member of the lute family. It has a body with a teardrop-shaped soundboard, or one which is essentially oval in shape, with a soundhole, or soundholes, of varying shapes which are open and are not decorated with an intricately carved grille like the Baroque era mandolins. Originally mandolins had six double courses of gut strings tuned similarly to lutes, and plucked with the fingertips, while the design common today has eight metal strings in four pairs (courses) which are plucked with a plectrum. The latter originated in Naples, Italy during the 3rd quarter of the 18th century.

Source wikipedia

A stringed instrument derived from the lute about 1700 in Italy. Of several kinds made in different cities, the Neapolitan mandolin became most popular. It has a deep, pear-shaped body and four pairs of steel strings tuned like a violin (G D A E, upward from the G below middle C). It is played with a plectrum, which creates the illusion of sustained tones by its rapid tremolo between the strings of each pair. The strings, hitched to a metal plate at the base of the body, run over a bridge and along the fretted fingerboard to machine-head tuning pegs. The belly angles down from the bridge to the base, increasing string tension for more brilliance of tone. The oval sound hole is surrounded by a protective shell plate.

Source encarta

Antonio Vivaldi, Mandolin Concerto, 1st Movement youtube video