Ruby is an open source, interpreted, object-oriented programming language, created in Japan by Yukihiro "Matz" Matsumoto and released in 1995, with the explicit goal of making programming enjoyable for developers. Its syntax is concise and close to natural language.
Its popularity comes mostly from Ruby on Rails, a web framework released in 2004 that set strong conventions ("convention over configuration") and makes it possible to build a complete application very quickly. GitHub, Shopify and Airbnb were largely built with Rails.
Ruby remains very present in startups and scale-ups that chose it early, especially for web and SaaS applications. It is less used for data, AI or heavy computation.
Why it matters when hiring
The Ruby talent pool is smaller than Python's or JavaScript's, which often lengthens searches. Two levers: target experienced Rails developers who know the scaling issues of an older application, or open the role to back-end profiles from other languages who are ready to learn. In interviews, check Rails knowledge beyond the generators: query performance, testing, breaking up a monolith.