Automated testing has been around for a very long time, with bespoke packages such as WinRunner, Rational Robot and QTP offering the most robust and proficient solutions when the world wide web was in its infancy and most applications were accessed via native windows based GUIs or the command line.
Modern applications generally run on internet based technology stacks that are cross-browser / cross-device compatible, requiring internet based test automation solutions that can act in the same way as a user on any of these browser / device combinations. Some of the first tools that leveraged the platform agnostic capabilities of these types of applications were Selenium (JavaScript) and Watir(Ruby based), both utilising JavaScript / COM based driver interfaces to emulate user browser actions.
WebDriver further extended the capabilities of both these tools using a JavaScript Driver Interface, providing a cleaner and simpler API with a bespoke driver for each commonly used browser (IE, Fire Fox, Chrome, Opera, etc.). Selenium became the defacto browser automation library of choice when I.E. was no longer supported by Microsoft, and has remained the market leader, with most test automation frameworks, including iterations of WATIR (6 and beyond) utilising it in combination with WebDriver to automate browsers through their own DSL test automation libraries. This detachment between browser automation and test automation scripting has meant that there are a myriad of options for the latter based on a combination of programming language + test automation framework.
Ruby + Cucumber + Selenium WebDriver is probably one of the best solutions for those new to test automation or who want to get things up and running without a steep learning curve associated with some programming languages.
However it is worth noting that Ruby programming skills are not as common or in demand as Python, Java or C#, when considering which framework to adopt to suit your team's test and development resources, in the long term.