I tend to use histograms of continuous variables adding estimated density curves in order to compare several charts easily. However, I find difficulties when I try to explain what density is and the interpretation of the curve's height to non-statisticians.
The stalwart Wikipedia provide us a good definition:
In probability theory, a probability density function (pdf), or density of a continuous random variable, is a function that describes the relative likelihood for this random variable to take on a given value.
Do you think the concept "relative likelihood" would be clear enough for non-statisticians? What is your approach in such situations?