How to interpret the different ggplot2 densities?

I am confused about the meaning of the following variants of geom_density in ggplot:

Can someone please explain the difference between these four calls:

1. geom_density(aes_string(x=myvar))
2. geom_density(aes_string(x=myvar, y=..density..))
3. geom_density(aes_string(x=myvar, y=..scaled..))
4. geom_density(aes_string(x=myvar, y=..count../sum(..count..)))

My understanding is that:

• geom_density alone will produce a density whose area under the curve sums to 1
• geom_density with ..density.. basically does the same... ?
• the ..count../sum(..count..) will normalize the peak heights to be more like a normalized histogram, ensuring that all the heights sum to 1
• the ..count.. by itself without the denominator will just multiply each bin by # of items in it
• the ..scaled.. parameter will make it so the maximum value of the density is 1.

I find ..scaled.. very counterintuitive and have never seen it used if my interpretation of it is correct so I'd like to ignore that. I am mainly looking for a clarification of the differences between geom_density and a kind of normalized density plot, which I am assuming requires the ...count../... argument. thanks.

(Related: Error with ggplot2 mapping variable to y and using stat="bin")