Every page access is logged in a student's history. The feedback system remembers graders' decisions for every submission for every student, down to the rubric item level. Reflections, fill-in-the-blank responses, etc., are all stored.
Skilling gathers other data as well. For example, Skilling asks students how hard each exercise was:
The data can help authors improve courses. For example, if most students thought that an exercise was easy, it might not be a good use of their time.
Privacy needs to be protected, however. Only administrators can export data. If authors want data for analysis, they have to request it from another person.
Further, identifying information, like students' names and email addresses, is stripped before data is exported. Students are identified by an id number in data exports. This lets authors and researchers check, for example, the relationship between procrastination and performance. However, the ids are meaningless internal numbers, that don't match anything in the real world.