The Violin is the highest-pitched memeber of the string family.
Tchaikovsky Violin Concerto played by the great Itzhak Perlman
Lindsey Stirling - Zelda Medley
Taylor Swift - Shake It Off
The Viola is the "alto" of the string family. It's not as high as the violin and it's not as low as the cello. While it may look just like the violin, it has a warmer sound than the violin and is often associated with more mysterious music.
Imagine Dragons - Demons
Leonard Cohen - Hallelujah
The Violinocello, or Cello for short, looks like a gigantic violin! The strings are the same as a Viola, just longer. The larger the instrument, the lower the sound, so the Cello is lower than the Violin and the Viola and has a very mellow sound. But, don't be fooled by the mellow cello. It can absolutely rock with the rest of them.
Yo-Yo Ma - The Swan from Carnival of the Animal
The Piano Guys - Cello Wars (Star Wars Parody) Lightsaber Battle
The Piano Guys - The Cello Song
The bass is the BIGGEST instrument in the string family. It's also the LOWEST-pitched. Often the bass is used as a time keeper for the orchestra, but advanced bass players can do some pretty cool and unique stuff with their instrument!
Seven Nation Army
The Elephant from Carnival of the Animals
Lorde - Royals