is an acronym for Modular Object-Oriented Dynamic Learning Environment

Moodle is a free and open-source software learning management system  distributed under the GNU General Public License

The stated philosophy of Moodle includes a constructivist and social constructionist approach to education, emphasizing that learners (and not just teachers) can contribute to the educational experience. Using these pedagogical principles, Moodle provides an environment for learning communities. Moodle has been translated in over 100 languages, and is available for any site administrator to install. People in various countries maintain and contribute to the various language packs.

Teaching with Moodle:  Demo resources

Documentation: Managing a Moodle course