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The heart of Moodle is courses that contain activities and resources. There are about 20 different types of activities available (forums, glossaries, wikis, assignments, quizzes, choices (polls), SCORM players, databases etc) and each can be customised quite a lot. The main power of this activity-based model comes in combining the activities into sequences and groups, which can help you guide participants through learning paths. Thus, each activity can build on the outcomes of previous ones.