With the Semesterticket you can use public transport in the Freiburg region

With the SemesterTicket, students can travel for an entire semester for only € 96 on the entire network of the Regio-Verkehrsverbund Freiburg (RVF).
The SemesterTicket is valid for all trams, buses and S-Bahn trains (2nd class/ no ICE and IC / EC trains) in the city of Freiburg as well as in the districts of Breisgau-Hochschwarzwald and Emmendingen. Students can therefore use it not only for trips to university, but also in their free time.

Without a SemesterTicket, the following applies: From 7:00 p.m. until closing time and on Sundays and public holidays, all students have free travel on RVF buses and trains. However, certain obligations to provide evidence also apply here.

More Infos here