Explaining about Types of Relationships & Difference b/w Master-Lookup Relationships?

A Relationship is connection b/w two objects.

In salesforce,there are 4 types of relationships here.

1. Look-up Relationship
2. Master Detail Relationship
3. Many to Many Relationship
4. Hierarchical Relationship

Relationships help us to who view,fetch information from one object to different objects.

Difference Between Master-Detail and Look-up Relationship's  as shown below :

Master-Detail Relationship :

1. Master-detail field value's are mandatory.
2. Values can be assigned only once and cannot be changed.
3. We can create maximum number of relationships are 2.
4. Cascading delete is an effect i,e if master-detail deleted,all the associate child records are also deleted automatically.
5. Master-detail cannot be created if records already exists.
6. Access rights are inherited to the child from the Master.

Look-Up Relationship :

1. Look-up field value's are not mandatory.
2. Values can be assigned any point of time and can be modified at anytime.
3. We can create upto 25 look-up relationships.
4. Cascading delete is not effect i,e If parent record is deleted,child record is not deleted.
5. Lookup can be create if records already exists.
6. Access rights are not inherited.