float $nz = 3* noise (nurbsPlane1ParticleShape.position*.1 + time);
nurbsPlane1ParticleShape.position = nurbsPlane1ParticleShape.position0 + <<0,$nz, 0>>;

Hi, that expression is used to control the y value of each particle in a grid of particles that has been parented to a nurbs plane. The result looks kind of like cloth blowing in the wind. What I don't understand is how the part that is in red can possibly be used to assign each particle its own y coordinate. Isn't position a vector attribute? How then can it yield a scalar value for $nz? And furthermore, how is it that it yields a different y value for each particle in the field?