Following information i found on msdn which might help you to understand difference you want
To retrieve global resources using strong typing
Resources.ResourceFile.ResourceName is used to retrieve global resources using strong typing
Resources are compiled into the namespace Resources, and each default resource becomes a member of the Resources class. For example, if you have created the default resource file WebResources.resx and the file contains a resource named WelcomeText, you can reference the resource in code as shown in the following code
String welcome;
welcome = Resources.WebResources.WelcomeText;
for more detail : http://msdn.microsoft.com/en-us/library/ms227982.aspx
Explicit Localization
<asp:Button ID="Button1" runat="server"
Text="<%$ Resources:WebResources, Button1
Caption %>
The resource expression takes the following form, where Class is optional, unless the resource is a global one, and ResourceID is required:
<%$Resources:Class,ResourceID%>
The Class value identifies the resource file to use when you use global resources. When .resx files are compiled, the base file name, without extensions, is used as the class name of the resulting assembly, explicitly. If you want to use resources from a local resource file (one that matches the current page name), you do not have to include a class name. This is because ASP.NET matches the page class to the resource class.
The ResourceID value is the identifier of the resource to read. In the previous example, the Text property for the button is read from the global resource file WebResources.resx (or the appropriate localized version). In that file, ASP.NET uses the value for the resource with the identifier Button1Caption and for the page itself. To set page properties, you can use resource expressions in the @ Page directive
more about this : http://msdn.microsoft.com/en-us/library/ms227427(v=VS.100).aspx