The violin family is fundamentally similar to the guitar except that it does not have frets. The violin family's strings are generally bowed rather than plucked, and to facilitate playing on one string with a bow, the strings are arrayed in an arc rather than a plane. A violin family instrument has only four strings rather than at least six found on a guitar. Violin family instruments are extremely popular for several reasons.
Violins are portable.
They don't need to be hooked up to anything. They are extremely responsive, meaning that they sound awful if you play badly and really good if you play well. They can be played in many different styles of musics, over many cultures. And they are fundamentally amazing. The body of a violin is so resonant at a wide range of frequencies, and the vibrations so well-coupled to the air that a single vibrating string, vibrating at a fraction of a millimeter in amplitude, can be heard loudly all the way to the back of an auditorium.