Master-Detail relationship is a relationship between a parent and child where the master represents the parent and the detail represents a child. This relationship can be used when we want to control the display of detail records based on the value present in the master record. The master object completely takes control of the behavior of the Detail object. The survival of the child is dependent on the parent, because if the parent gets deleted then the child automatically gets deleted. You can create Roll-up summary fields in master records which will calculate the SUM, AVG, and MIN of the child records. Consider an example of a courier company model, where a delivery schedule is always linked to a delivery location. If we delete a delivery location from our list, then all the related delivery schedules should also be removed. Such a dependency can be achieved only through a Master-Detail relationship.