What is "duolingo"

Duolingo ( or ) is a free language-learning platform that includes a language-learning website and app, as well as a digital language proficiency assessment exam. Duolingo offers all its language courses free of charge. As of April 2016, the language-learning website and app offer 59 different language courses across 23 languages; with 23 additional courses in development. The app is available on iOS, Android and Windows 8 and 10 platforms with about 120 million registered users across the world.