What's the value of y axis?

I’m copying my answer from mRNA expression (RNAseq) scatter plot issues - #10 by pmontgom in case people have the same question and come across it here:

The y value within a violin plot is randomly assigned. The points are “jittered” on the y-axis to avoid overplotting and allow you to see individual points. There is no meaning to the y-value within each violin.

Thanks,
Phil