In short, resource files are used to store things, from text to images. Resource files can be targeted to different locales.You would essentially have a resource file for every locale (or language) you wish to support. In your case, you'd need two, one for English and one for French.
Here's an MSDN tutorial describing the process step-by-step:
http://msdn.microsoft.com/en-us/library/y99d1cd3(v=vs.100).aspx[
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