answer:It might differ per university (so be sure to check the website of the university you want to attend) and where you live (Europe?), but the way it works for mine (Utrecht University) is that a major is obligatory (this is the actual track you follow), and next to your major you have some “free” time slots to fill with courses you’d like to enrol in that aren’t necessarily part of your major. Minors, then, are “packages” of courses that are picked such that they are related. If you take part in a minor, you put the courses part of that minor in your free time slots. It is then easy for some masters to only allow students from specific majors or students from some majors that have also completed a certain minor. Thus, they don’t have to evaluate each student’s chosen courses to see if he/she has the required knowledge to be able to get along.