Post graduates are students who have earned an undergraduate degree from any institution and wish to take graduate-level courses. They are seeking credit, but not towards a specific graduate degree program.
Undergraduate guest students are students who have earned an undergraduate degree from any institution and wish to take undergraduate-level courses. This also includes students who have graduated from high school, but do not wish to enroll in a full program. In either instance, students are seeking credit, but not toward a specific undergraduate degree program.