Wind in the Trees

My camera lets me do 3 multiple exposures and combines them itself. So I did that twice and then combined the two resulting images in photoshop (The first time I've played "properly" with Ps). This was inspired by my tutor Paul D who talked about this idea.
I did use a tripod so the movement is purely down to the wind in the trees!
Does anyone know what all the different blending modes in photoshop do?