The Google Translate API is a powerful tool that can be used to translate text from one language to another, with support for detecting the language of the input text and providing accurate translations. To use this API in a Ruby on Rails application, developers need to create an account on RapidAPI, subscribe to the API, and install the necessary dependencies, including Excon and i18n_data gems. The API can be used to translate text by sending a POST request to the `language/translate/v2` endpoint with the source text and destination language codes. The response from the API includes the translated text. To implement this in a Ruby on Rails application, developers need to create a controller that handles the translation requests, including setting up the form fields for the user input, handling the form submission, and rendering the translated text. The `api_request` method is used to send the request to the Google Translate API, and the `fetch_languages` method is used to retrieve the list of available languages from the API.