Implementing internationalization (i18n) in a Gatsby site is a straightforward process that enhances user experience by serving content in multiple languages, allowing for cultural nuances that automated translation tools like Google Translate cannot capture. The process involves replacing hard-coded strings with variables that switch language based on user preference, using language codes and locales to manage different versions of a language, such as American and British English. Collaborating with professional translators, such as Applingua, ensures accuracy and consistency in translations, while react-i18next is a preferred package due to its documentation and compatibility with existing systems. Setting up i18n involves creating a folder structure for translation strings, configuring the Gatsby setup to handle these translations, and using higher-order components (HOCs) to manage language switching in components. The guide also offers tips on using translation strings for page titles with React Helmet and creating components for seamless language switching, ultimately demonstrating that with the right setup, serving international users on a Gatsby site is efficient and manageable.