Hands back, create separation

If you ask Brian Castonguay what separation is, he'll give you an expalnation like this.

Stride and Separate.
You will stride forward in a very controlled and soft movement, while using your shoulder and outside oblique to pull the top half of your body in the opposite direction.

Tension.
Once your front foot hits the ground and your hands remain back from where the load took them, this will create tension in your front oblique area.

This tension is like a stretched rubber band that will allow for a violent action toward the baseball. The more stretched tension you create, the more bat speed you can create.