[boltzmann64]

When you throw a balloon of colored water at a wall, the impression it makes on the wall is called a splat. Say you have a function which takes a point in 3d and outputs a density value which goes to zero as you move away to infinity from the from the functions location (mean) like a bell curve (literally), and you throw (project) that function to plane (your camera film), you get a splat.

Note: I've made some simplifying assumption in the above explanation.