When we introduced unit structure we presented the hierarchy of content in ARK as:
The smallest unit in the hierarchy is either a resource or an activity.
A resource is a piece of static, ungraded content designed to present information to the student.
An activity is an item that the student interacts with, either individually or with other students. Some activities can be graded and may contribute to the gradebook.
Teachers can add activities and resources to their units using the activity chooser. To access the activity chooser, enable editing and click Add an activity or resource at the bottom of a section.
When you first open the Activity Chooser, you will see four tabs: All, Activities, Resources and Recommended.
The Recommended tab contains a shortlist of activities and resources recommended at the University of Divinity.
You can star your favourite or frequently used activities and resources and they will show in the Starred tab.
The activity icons are colour-coded according to their various functions:
See the MoodleDocs page for more information: Activity Chooser (4.1)