It uses density curves to indicate distributions of numeric data for one or more sets, and the frequency of data points in each region is portrayed by the width of each curve.

Violin plots are composed of:

• median - white dot on the violin
• interquartile range - black bar in the center of violin
• lower/upper adjacent values - the black lines stretched from the bar

The usage of violin plots

Violin plots are a good choice when observing the distribution of numeric data, and they are particularly great when comparing distributions between multiple groups. 

Violin plot vs. box plot

Violin plots deliver much more information than box plots. They allow, for example, to indicate if the distribution is bimodal or multimodal.