Difference between "BUILTIN\Administrators" and "MachineName\Administrators"

Hi,


Sorry for inefficiency in english.


I tried to apply the role based authorization in windows authenticaiton in web.config by using the code:


     <authorization>
            <allow roles="MachineName\Users"/>
            <deny roles="BUILTIN\Administrators"/>
     </authorization>


As the "Administrators" group is working with "BuiltIn" not with "MachineName".

I need to know that what is the differene in using "BuiltIn" in place of "MachineName".

I am applying the role based authorization for the groups of my local system.


It's become a headache for me as I am not able to undetstand that what should I have to use with group name ...