Explain “Master-Detail Relationship” in Salesforce ?

Master-Detail Relationship is the Parent child relationship. In which Master represents Parent and detail represents Child.In this relationship,if parent is deleted then Child also gets deleted.
Rollup summary fields can only be created on Master records which will calculate the SUM, AVG, MIN of the Child records.

• Up to 2 Master-Detail Relationships are allowed to an object.
• Parent field on child is required.
• Access to parent determines access to children.
• Deleting parent automatically deletes child.
• A child of one master detail relationship cannot be the parent of another.
• Lookup field on page layout is required.