During installation, WSN offers a list of languages to choose from. If you select only the English option, you'll end up with an english-only website where the templates are filled with english text for easier reading, but which cannot be translated. If you'll ever want to use a language other than english, be sure to specify it during the install -- if your desired language isn't pre-supplied, write it in the "other" box. If any non-english language is selected, you'll get a multilingual installation where the templates are filled with language variables and all the text you need to translate is accessible via Admin -> Customizations -> Language.

Some points to consider:

• You can install multiple languages.
  
• If you plan to distribute a theme to others, be sure you're using multilingual. English-only themes are autogenerated from multilingual, but not vice versa.
  
• Multilingual takes the language out of the templates. The result is that templates are filled with language variables and not as easy to read, however chaning language is quicker since it's done all at once through the language section, and you can handle two languages with the same templates.
  
• The templates used by the multilingual version can be found in your templates/multilingual directory. English-only templates are in templates/default.
  
• Even with English-only, there will still be items in your language section. These include outgoing emails, page titles, and various other things which cannot logically fit into a template.
  
• English-only templates are much easier to recogize and find your way around in since all the text is written in directly... however you will tend to lose more of your customized text on upgrades because of this.
  
• If you edit your templates offline in a WYSIWYG editor such as FrontPage or DreamWeaver, it will be much more comprehensible with the English-only templates due to the smaller number of template variables.