Moodle activities provides a number of powerful-collaborative activity modules & tools which enable you to link or add almost any sort of file to your course. There are many different types of activities that are available: several types-of assignments; activities for communication & collaboration between you & your students; surveys, quizzes and polls; tools to help in managing the students; & formats for delivering-interactive content.
An activity is the general term that is used to refer to a group-of features in the Moodle course. Basically an activity is some thing which a student does which interacts with the other students or/and the teacher
Via Miloš Bajčetić