Each violin is made of several types of wood. The most common types of wood used are maple (back, ribs, neck and scroll), spruce (front) and ebony (pegs, fingerboard, tailpiece and end button). Other woods that might be used include willow and rosewood. The standard wood used to make a bow is pernambuco wood.
What's the difference between a violin and viola? Well, despite the obvious difference in size (viola is bigger), the viola has different strings (C, G, D, A...same as cello) and uses a completely different clef - alto clef.