Localizing ASP.NET Web Pages By Using Resources

Resource Files:
A resource file is an XML file that contains the strings that you want to translate into different languages or paths to images. The resource file contains key/value pairs. Each pair is an individual resource. Key names are not case sensitive.
You create a separate resource file for each language (for example, English and French) or for a language and culture (for example English [U.K.], English [U.S.]). Each localized resource file has the same key/value pairs; the only difference is that a localized resource file can contain fewer resources than the default resource file.

List of Culters:
Resource files in ASP.NET have an .resx extension. At run time, the .resx file is compiled into an assembly, which is sometimes referred to as a satellite assembly. Because the .resx files are compiled dynamically, like ASP.NET Web pages, you do not have to create the resource assemblies. The compilation condenses several similar-language resource files into the same assembly.
When you create resource files, you start by creating a base .resx file. For each language that you want to support, create a new file that has the same file name. But in the name, include the language or the language and culture (culture name).
At run time, ASP.NET uses the resource file that is the best match for the setting of the CurrentUICulture property. The UI culture for the thread is set according to the UI culture of the page. For example, if the current UI culture is Spanish, ASP.NET uses the compiled version of the WebResources.es.resx file. If there is no match for the current UI culture, ASP.NET uses resource fallback. It starts by searching for resources for a specific culture. If those are not available, it searches for the resources for a neutral culture. If these are not found, ASP.NET loads the default resource file.