Unlike its predecessors, the viol and the viola da gamba, the violin has no frets on the fingerboard, so the player has to learn where the pitches are. You can see the difference by comparing the neck of the violin with the neck of a standard guitar.
The same pitch on the violin can often be found on more than one string. For instance the pitch of the D that is the open string on the second to lowest string can also be found in a higher position on the lowest string, the G string.
