The Library has certain resources that, per license agreements, are available to current students. Because it was decided that those resources should be available to students between semesters and over the summer if they were coming back.
That lead to a "Current Student Role", known internally in Banner as CURSTUDENT. Since it's creation, it has been used for several more purposes. It is also controlled automatically by Banner.
The precise definition is a student is classified as a "Current Student" if he or she has been enrolled recently enough to not be required to be re-admitted to enroll again. In simple terms, a student is required to be re-admitted if they sit out a fall or spring semester. Because it is traditional, re-admission is not required if they sit out a summer.
In recent years, the increase in "parts of term" where courses begin at many points through a semester, a student could be enrolled in the spring and then next enroll in a class that starts in November and not require re-admission.
Because of situations like that, the Current Student Role definition has been changed such that it is re-evaluated at the end of the fall and spring semesters and students who did not enroll in that semester are removed from the Current Student Role.