A minor is a set of coherent courses related to the same subject. A minor is usually 30 EC. Utrecht University offers over 100 programme specific as well as multidisciplinary minors.
You can choose a minor as part of your academic profiling. It is a good way to deepen your knowledge of a certain discipline that interests you. It may also serve as a good preparation, or even entry requirement, for the Master's programme that you wish to do.
You should begin planning your minor in time. If you want to do a minor that does not fit in with the rest of your programme, you might substitute a course for a course outside the minor. You should always consult the Study Advisor on this. Make sure you register for the minor and for each course of the minor. Some minors have entry requirements.
Generally you can do any of the minors offered by Utrecht University. Unfortunately most of them are in Dutch. It is possible to search by language of instruction, start period, area of interest or faculty.