How to read the y-axis in geom_denisty plots?

[Steen_Harsted]

I am unsure how to read the y-axis of density plots produced using geom_density()

I understand the purpose of a Kernel density plot, but I find the range values confusing.

E.g., what do the numbers on the y-axis in the below example mean?

Thanks in advance.

library(ggplot2)

ggplot(diamonds, aes(carat, fill = cut)) +
  geom_density(position = "stack")

^{Created on 2020-01-22 by the reprex package (v0.3.0)}