Ruby is predominantly used as a backend object-oriented programming (OOP) language, designed to manage server-side operations and communicate with databases in a web application. With the Ruby on Rails framework, Ruby is often used to build robust and scalable backend architectures. However, it's worth noting that while Ruby itself isn't used for front-end development, full-stack Ruby developers might also work with front-end technologies like HTML, CSS, and JavaScript to create a seamless user experience.