A student's "major" at a university is a group of courses which make up a defined program of study designed to demonstrate both scope and depth in a field of study.  It usually includes 6-7 courses that are expressly required by the academic department, and then also requires 3-6 courses that are electives, i.e., courses chosen from a selection of 10 or more possible courses available to supplement the core requirements.

are the main subjects that a person studies at school - Science, Math, History, Language Arts, etc