After you have bound skin, you might decide that you want to modify the skeleton, change the bind pose, or do some further modeling on the skin. To do these things you must first detach the skin from the skeleton, then bind the skin again.
Detaching skin does not preserve the rigid skin point sets and the rigid skin point weights. If you want to preserve the rigid skin point sets, see Detach and reattach to skeletons and Detach and reattach to selected joints.