A Fiddle with pretensions of grandeur. Actually, there is no difference between the Fiddle and the Violin as Instruments, only how they are played.
A Four-stringed musical instrument tuned in fifths (GDAE), played with a bow, and held between the shoulder and the chin. It is fretless making it a) initially harder to play and b) more expressive than an equivalent fretted instrument such as a Mandolin.
Probably derived from a fusion of the Rebec, the Lira Da Braccio and the Renaissance Fiddle in the 16th century, it reached its peak in the 17th century and was modified to modern form in the 18th century.
Violins are built in different sizes given fractional names such as 7/8 or 3/4 or 1/2. These are not actual proportional sizes. A full size will have a 14 inch body and a half size will have a 12 inch body.
Strings were originally gut (sheep or rat - not cat) but now tend to be metal or synthetic.
The bow is made with horsehair which has to be rosined. The hair has small hooks on which scratch against the strings causing them to vibrate. The rosin is a kind of pine resin and dragging the bow hair through it causes the tiny hooks to stand up and stay up.
Image from 8Notes.com