Duolingo is a website where you can take courses in several languages. Each lesson uses a variety of different learning methods to help make sure the lessons stick.
Con The hype in the community creates false ideas about what level Duolingo gets you to
Duolingo is a good tool for a beginner, and a good supplement to other resources. But it cannot get you from zero to understanding natives, tv, and books; and their "do the reverse tree and just speak" is usually not the correct answer to "what should I do after finishing the tree".
Con Available languages are predominately European
Duolingo teaches 23 languages from English at the moment: Latin American Spanish, French, German, Italian, Portuguese, Dutch, Swedish, Irish, Turkish, Danish, Russian, Norwegian, Esperanto, Ukrainian, Polish, Welsh, Greek, Romanian, Hungarian, Hebrew, Swahili, Vietnamese and Japanese (the last currently only on the app). Popular non-European languages such as Mandarin and Arabic are not currently available (although Korean and Indonesian are in development).