Internationalization for Your WordPress Theme — SitePoint

WordPress is used to create a variety of types of websites. When building a WordPress theme, you should build it for as large of an audience as possible. That goal also implies that your theme should be ready for sites in different languages. WordPress provides a simple API that you can use in a theme to provide internationalization for it. In this article, you will see how you can make your theme ready for different languages. How to Configure WordPress for Different Languages
You can add different languages to your WordPress site. For that, you can download the translation files from the blog of the WordPress translator team. From this page, you can see the various languages whose translations are present, as well as what percentage of the translation is complete. Suppose I want to download the French language. I will go to the French language row, then click on the percentage as shown in the image below.
Then, you can click on the WordPress version, and export the .mo file as shown in the image below
Once you have downloaded the .mo file, you will have to upload it to the wp-content/languages folder of your WordPress installation. You can then go to the Settings -> General in
Source: https://managewp.org/articles/15442/internationalization-for-your-wordpress-theme-sitepoint

source https://williechiu40.wordpress.com/2017/06/30/internationalization-for-your-wordpress-theme-sitepoint/