How can i know the relationship between Standard objects?

Hi Suraj,

You can achieve this by using Schema Builder in Salesforce.Search for Schema Builder in Quick find Box.Now on the left side click on all those objects among whom you wan't to see the relationship.For example to see the relationship among Account , contacts and Cases you will achieve something like this :

You can also do this by checking the fields of these objects and seeing their Lookup relationships.But this would be a lengthy approach.So better use Schema Builder.

Thanks.