What exactly does semester hours mean?

In brief, it means the number of hours of class contact time per week for the length of the semester. One credit equals 16 hours of class contact time for the semester which is typically broken down to one hour of class contact time per week. Thus, a three credit course would equal 48 hours of class contact time for the length of the semester and that is typically broken down into three hours per week for the length of the semester.