Need to know the meaning of each element in CAS Policy xml?

Question

Hi,

below is the XML for CAS Policy , can somebody please explain me the meaning of each element in below xml in more simple language.

<CodeAccessSecurity>

<PolicyItem>

      <PermissionSet        class="NamedPermissionSet"        version="1"       Description="Permission set for custom test WebParts">  

        <IPermission            class="AspNetHostingPermission"            version="1"            Level="Minimal"          />   

       <IPermission            class="SecurityPermission"            version="1"            Flags="Execution"          />    

      <IPermission            class="Microsoft.SharePoint.Security.SharePointPermission,              Microsoft.SharePoint.Security, version=11.0.0.0,              Culture=neutral, PublicKeyToken=71e9bce111e9429c"            version="1"            ObjectModel="True"           />    

      <IPermission            class="System.Net.WebPermission, System,              version=1.0.5000.0, Culture=neutral,              PublicKeyToken=b77a5c561934e089" version="1">     

      <ConnectAccess>             <URI uri="https?://.*" />         

  </ConnectAccess>       

  </IPermission>       

   <IPermission            class="System.Security.Permissions.SecurityPermission,              mscorlib, version=1.0.5000.0, Culture=neutral,              PublicKeyToken=b77a5c561934e089"            version="1"            Flags="ControlThread, UnmanagedCode"          />          <IPermission            class="System.Security.Permissions.EnvironmentPermission,              mscorlib, version=1.0.5000.0, Culture=neutral,              PublicKeyToken=b77a5c561934e089"            version="1"            Read="UserName"          />   

    </PermissionSet>   

   <Assemblies>  

      <Assembly PublicKeyBlob=PublicKeyBlob />  

    </Assemblies>   

 </PolicyItem>

 </CodeAccessSecurity>

thanks

gaurav