In a Master–Detail relationship, when a Master record is deleted, the Detail record also gets deleted, automatically. On the other hand, in a Lookup relationship, the Child record will not be deleted, even if the Parent record is deleted.
In a Master–Detail relationship, when a Master record is deleted, the Detail record also gets deleted, automatically. On the other hand, in a Lookup relationship, the Child record will not be deleted, even if the Parent record is deleted.