When should I use SPSecurity.RunWithElevatedPrivileges?

It is very importent to understand why and when to use SPSecurity.RunwithElevatedPrivilages.When we want to retrive or update the data where a normal user don't have permission,there we use this code segment. How this exactly works is like SPSecurity.RunWithElevatedPrivileges runs current process under application pool identity and it allows users to add/update item in list,library or site.


Example 

SPSecurity.RunWithElevatedPrivileges(delegate()
{
    using (SPSite site = new SPSite(web.Site.ID))
    {


      // site will be based on the rights for the system account

    }

});

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