Duolingo is a free language-learning and crowdsourced text translation platform.
It is available on the Web, iOS, Android and Windows Phone 8.1 platforms.
Duolingo provides extensive written lessons and dictation, with speaking practice for more advanced users. It has a gamified skill tree that users can progress through and a vocabulary section where learned words can be practiced.
Users gain "experience points" as they learn a language, such as when they complete a lesson. Skills are considered "learned" when users complete all the lessons associated with the skill.
Duolingo uses a data-driven approach to lesson planning. At each step along the way, the system measures which questions the users struggle with and what sorts of mistakes they make.
By using algorithms to estimate how well users work on an exercise, people who fare better will get different questions than those that find experience difficulty in the Duolingo classes.
Language software packages can only supplement a course in a language school. A software package can help to memorize new words and practice familiar grammar. If you want English words and grammar rules to develop into a coherent speech, it is preferable to study in a reliable language school with professional native teachers.