When do I need al.exe (Assembly Linker)?

I am reading about localization and there is one topic that I don't really understand. The book I am reading (Developing ASP.Net MVC 4 Web Applications) says that I can use Assembly Linker (al.exe) to create assembly assemblies from .resx files so that the application gets some performance boost instead of read directly from the file.

He then gives me an example of how I can create these satellite assemblies via Visual Studio Command Prompt

using Assembly Linker

. But why would I do this? When I create an application, folders are created in the bin folder containing the DLLs for each language I have created, which are .resx files. How en-US/project.resources.dll

.

Am I missing something or not, are these satellite assemblies referenced when used al.exe

to create satellite assemblies? What can do al.exe

that Visual Studio doesn't do when building an app?