What is the difference between the Merger Rule and the Moving Boundaries Rule?

What will be an ideal response?

Merger Rule is the legal rule that the treaties in effect in a former state remain in effect in its territory when it becomes part of a new state. If territory from one state shifts to another, the law of state succession applies the Moving Boundaries Rule. This holds that the treaties of the absorbing state displace the treaties of the receding state in the territory where sovereignty has changed.