Selenium-Webdriver is a tool for writing automated tests of websites. It provides Ruby bindings that allow testing a website's functionality across multiple browsers. It supports browsers like Internet Explorer, Firefox, Safari, Opera, and Chrome. Selenium-Webdriver allows finding elements on a page by class name, css selector, id, link text, name, partial link text, tag name, or xpath. It also supports manipulating the browser window by resizing or maximizing it. Javascript execution and switching between frames are also capabilities. Waiting for elements to load is supported through explicit and implicit waits.