Osiris is the student information system, that records all student data, from enrollment right through to graduation. You can use Osiris to view your grades, register for courses and examinations, and to keep track of your progress. If you have more questions you can contact the Education and Student Affairs (ESA) office at the Metaforum/Library or you can contact them by email at ESA@tue.nl
It is important to note the deadlines for course registration, which is usually a month before the coming quartile. If you have not managed to register for your course before the deadline, you will have to pay an administrative cost of €20 for each course you want to register to after the deadline. More information can be found here.
Elective courses are courses you take outside the study package of your faculty. To register for an elective course you first need to have the elective package approved by the Examination Committee, this can be done by contacting the study advisor of your faculty.
Osiris also has a PlanApp to help you plan your courses during your study period. This tool is very helpful because it shows the timeslots of each course and whether a course will clash with another course you are taking.