The Site Language configuration option of WordPress allows you to select the language that will be seen by visitors when they go to your website. As can be seen in the drop-down list of languages, WordPress has a single language installed by default, shown at the top of the list. The remainder of the list indicates languages that can be added to your website. When you set a new language, translation files are automatically downloaded for the selected language and the new selection becomes the default for visitors. If you look inside the wp-content/languages directory of your WordPress installation, you will see that a number of files with .po and .mo extensions were downloaded for the selected language. Portable object (.po) files are ASCII text files that contain a list of all the original English text from the WordPress source code, while machine object (.mo) files are binary versions of the translation table that have been compiled to be efficiently loaded by PHP as a website is rendered.