No, Selenium does not necessarily translate Java into JavaScript or similar languages.
According to information from http://docs.seleniumhq.org/docs/03_webdriver.jsp:
Selenium-WebDriver directly communicates with the browser using each
browser’s built-in automation support. The specific features and methods used depend on the particular browser being automated.
The Selenium WebDriver contains a component that is customized for each browser and is typically integrated as a module, extension, or plugin within the browser itself. This component provides an interface for interacting with the Selenium script written in Java, for example.
The way this plugin interacts with the browser varies depending on its implementation. Most likely, developers would try to avoid compiling Java code to JavaScript first, as it could be inefficient. Instead, they would opt to utilize the browser's internal APIs to directly access and manipulate the DOM whenever possible.